Add main-thread scrolling reasons to "Scrolling performance issues"

The inspector has a feature for "Scrolling performance issues" under the
bottom console's "Rendering" tab which shows reasons for non-fast
scrolling. This feature did not include main-thread scrolling reasons
such as background-attachment: fixed. This patch adds main-thread
scrolling reasons to the scrolling performance issues visualization.

Bug: 1015918
Change-Id: I46039b4fc8ba3400cab1c2633da31e427865ce3d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1868660
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Auto-Submit: Philip Rogers <pdr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709113}

cc/debug/debug_colors.cc

@@ -276,6 +276,17 @@ SkColor DebugColors::NonFastScrollableRectFillColor() {
   return SkColorSetARGB(30, 238, 163, 59);
 }
 
+// Main-thread scrolling reason rects in yellow-orange.
+SkColor DebugColors::MainThreadScrollingReasonRectBorderColor() {
+  return SkColorSetARGB(255, 200, 100, 0);
+}
+int DebugColors::MainThreadScrollingReasonRectBorderWidth() {
+  return 2;
+}
+SkColor DebugColors::MainThreadScrollingReasonRectFillColor() {
+  return SkColorSetARGB(30, 200, 100, 0);
+}
+
 // Animation bounds are lime-green.
 SkColor DebugColors::LayerAnimationBoundsBorderColor() {
   return SkColorSetARGB(255, 112, 229, 0);

cc/debug/debug_colors.h

@@ -104,6 +104,10 @@ class CC_DEBUG_EXPORT DebugColors {
   static int NonFastScrollableRectBorderWidth();
   static SkColor NonFastScrollableRectFillColor();
 
+  static SkColor MainThreadScrollingReasonRectBorderColor();
+  static int MainThreadScrollingReasonRectBorderWidth();
+  static SkColor MainThreadScrollingReasonRectFillColor();
+
   static SkColor LayerAnimationBoundsBorderColor();
   static int LayerAnimationBoundsBorderWidth();
   static SkColor LayerAnimationBoundsFillColor();

cc/debug/layer_tree_debug_state.cc

@@ -21,6 +21,7 @@ LayerTreeDebugState::LayerTreeDebugState()
       show_wheel_event_handler_rects(false),
       show_scroll_event_handler_rects(false),
       show_non_fast_scrollable_rects(false),
+      show_main_thread_scrolling_reason_rects(false),
       show_layer_animation_bounds_rects(false),
       slow_down_raster_scale_factor(0),
       rasterize_only_visible_content(false),
@@ -50,6 +51,7 @@ bool LayerTreeDebugState::ShowHudRects() const {
          show_surface_damage_rects || show_screen_space_rects ||
          show_touch_event_handler_rects || show_wheel_event_handler_rects ||
          show_scroll_event_handler_rects || show_non_fast_scrollable_rects ||
+         show_main_thread_scrolling_reason_rects ||
          show_layer_animation_bounds_rects || show_layout_shift_regions;
 }
 
@@ -71,6 +73,8 @@ bool LayerTreeDebugState::Equal(const LayerTreeDebugState& a,
       a.show_wheel_event_handler_rects == b.show_wheel_event_handler_rects &&
       a.show_scroll_event_handler_rects == b.show_scroll_event_handler_rects &&
       a.show_non_fast_scrollable_rects == b.show_non_fast_scrollable_rects &&
+      a.show_main_thread_scrolling_reason_rects ==
+          b.show_main_thread_scrolling_reason_rects &&
       a.show_layer_animation_bounds_rects ==
           b.show_layer_animation_bounds_rects &&
       a.slow_down_raster_scale_factor == b.slow_down_raster_scale_factor &&
@@ -96,6 +100,8 @@ LayerTreeDebugState LayerTreeDebugState::Unite(const LayerTreeDebugState& a,
   r.show_wheel_event_handler_rects |= b.show_wheel_event_handler_rects;
   r.show_scroll_event_handler_rects |= b.show_scroll_event_handler_rects;
   r.show_non_fast_scrollable_rects |= b.show_non_fast_scrollable_rects;
+  r.show_main_thread_scrolling_reason_rects |=
+      b.show_main_thread_scrolling_reason_rects;
   r.show_layer_animation_bounds_rects |= b.show_layer_animation_bounds_rects;
 
   if (b.slow_down_raster_scale_factor)

cc/debug/layer_tree_debug_state.h

@@ -41,6 +41,7 @@ class CC_DEBUG_EXPORT LayerTreeDebugState {
   bool show_wheel_event_handler_rects;
   bool show_scroll_event_handler_rects;
   bool show_non_fast_scrollable_rects;
+  bool show_main_thread_scrolling_reason_rects;
   bool show_layer_animation_bounds_rects;
 
   int slow_down_raster_scale_factor;

cc/input/main_thread_scrolling_reason.cc

@@ -5,6 +5,7 @@
 #include "cc/input/main_thread_scrolling_reason.h"
 
 #include "base/stl_util.h"
+#include "base/strings/string_util.h"
 #include "base/trace_event/traced_value.h"
 
 namespace cc {
@@ -19,6 +20,8 @@ std::string MainThreadScrollingReason::AsText(uint32_t reasons) {
   result =
       result.substr(array_start_pos + 1, array_end_pos - array_start_pos - 1);
   base::Erase(result, '\"');
+  // Add spaces after all commas.
+  base::ReplaceChars(result, ",", ", ", &result);
   return result;
 }
 

cc/input/main_thread_scrolling_reason_unittest.cc

@@ -13,26 +13,26 @@ using MainThreadScrollingReasonTest = testing::Test;
 TEST_F(MainThreadScrollingReasonTest, AsText) {
   EXPECT_EQ("", MainThreadScrollingReason::AsText(0));
   EXPECT_EQ(
-      "Has background-attachment:fixed,"
-      "Has non-layer viewport-constrained objects,"
-      "Threaded scrolling is disabled,"
-      "Scrollbar scrolling,"
-      "Frame overlay,"
-      "Handling scroll from main thread,"
-      "Has opacity and LCD text,"
-      "Has transform and LCD text,"
-      "Background is not opaque in rect and LCD text,"
-      "Has clip related property,"
-      "Has box shadow from non-root layer,"
-      "Is not stacking context and LCD text,"
-      "Non fast scrollable region,"
-      "Failed hit test,"
-      "No scrolling layer,"
-      "Not scrollable,"
-      "Continuing main thread scroll,"
-      "Non-invertible transform,"
-      "Page-based scrolling,"
-      "Wheel event handler region,"
+      "Has background-attachment:fixed, "
+      "Has non-layer viewport-constrained objects, "
+      "Threaded scrolling is disabled, "
+      "Scrollbar scrolling, "
+      "Frame overlay, "
+      "Handling scroll from main thread, "
+      "Has opacity and LCD text, "
+      "Has transform and LCD text, "
+      "Background is not opaque in rect and LCD text, "
+      "Has clip related property, "
+      "Has box shadow from non-root layer, "
+      "Is not stacking context and LCD text, "
+      "Non fast scrollable region, "
+      "Failed hit test, "
+      "No scrolling layer, "
+      "Not scrollable, "
+      "Continuing main thread scroll, "
+      "Non-invertible transform, "
+      "Page-based scrolling, "
+      "Wheel event handler region, "
       "Touch event handler region",
       MainThreadScrollingReason::AsText(0xffffffffu));
 }

cc/layers/heads_up_display_layer_impl.cc

@@ -1031,6 +1031,14 @@ void HeadsUpDisplayLayerImpl::DrawDebugRects(
         stroke_width = DebugColors::NonFastScrollableRectBorderWidth();
         label_text = "repaints on scroll";
         break;
+      case MAIN_THREAD_SCROLLING_REASON_RECT_TYPE:
+        stroke_color = DebugColors::MainThreadScrollingReasonRectBorderColor();
+        fill_color = DebugColors::MainThreadScrollingReasonRectFillColor();
+        stroke_width = DebugColors::MainThreadScrollingReasonRectBorderWidth();
+        label_text = "main thread scrolling: ";
+        label_text.append(base::ToLowerASCII(MainThreadScrollingReason::AsText(
+            debug_rects[i].main_thread_scrolling_reasons)));
+        break;
       case ANIMATION_BOUNDS_RECT_TYPE:
         stroke_color = DebugColors::LayerAnimationBoundsBorderColor();
         fill_color = DebugColors::LayerAnimationBoundsFillColor();

cc/trees/debug_rect_history.cc

@@ -50,6 +50,9 @@ void DebugRectHistory::SaveDebugRectsForCurrentFrame(
   if (debug_state.show_non_fast_scrollable_rects)
     SaveNonFastScrollableRects(tree_impl);
 
+  if (debug_state.show_main_thread_scrolling_reason_rects)
+    SaveMainThreadScrollingReasonRects(tree_impl);
+
   if (debug_state.show_layout_shift_regions)
     SaveLayoutShiftRects(hud_layer);
 
@@ -205,4 +208,23 @@ void DebugRectHistory::SaveNonFastScrollableRectsCallback(LayerImpl* layer) {
   }
 }
 
+void DebugRectHistory::SaveMainThreadScrollingReasonRects(
+    LayerTreeImpl* tree_impl) {
+  const auto& scroll_tree = tree_impl->property_trees()->scroll_tree;
+  for (auto* layer : *tree_impl) {
+    if (layer->scrollable()) {
+      if (const auto* scroll_node =
+              scroll_tree.Node(layer->scroll_tree_index())) {
+        if (auto reasons = scroll_node->main_thread_scrolling_reasons) {
+          debug_rects_.push_back(DebugRect(
+              MAIN_THREAD_SCROLLING_REASON_RECT_TYPE,
+              MathUtil::MapEnclosingClippedRect(layer->ScreenSpaceTransform(),
+                                                gfx::Rect(layer->bounds())),
+              kTouchActionNone, reasons));
+        }
+      }
+    }
+  }
+}
+
 }  // namespace cc

cc/trees/debug_rect_history.h

@@ -46,26 +46,32 @@ enum DebugRectType {
   WHEEL_EVENT_HANDLER_RECT_TYPE,
   SCROLL_EVENT_HANDLER_RECT_TYPE,
   NON_FAST_SCROLLABLE_RECT_TYPE,
+  MAIN_THREAD_SCROLLING_REASON_RECT_TYPE,
   ANIMATION_BOUNDS_RECT_TYPE,
   LAYOUT_SHIFT_RECT_TYPE,
 };
 
 struct DebugRect {
   DebugRect(DebugRectType new_type,
             const gfx::Rect& new_rect,
-            TouchAction new_touch_action)
-      : type(new_type), rect(new_rect), touch_action(new_touch_action) {
+            TouchAction new_touch_action = kTouchActionNone,
+            uint32_t main_thread_scrolling_reasons = 0)
+      : type(new_type),
+        rect(new_rect),
+        touch_action(new_touch_action),
+        main_thread_scrolling_reasons(main_thread_scrolling_reasons) {
     if (type != TOUCH_EVENT_HANDLER_RECT_TYPE)
       DCHECK_EQ(touch_action, kTouchActionNone);
+    if (type != MAIN_THREAD_SCROLLING_REASON_RECT_TYPE)
+      DCHECK(!main_thread_scrolling_reasons);
   }
-  DebugRect(DebugRectType new_type, const gfx::Rect& new_rect)
-      : DebugRect(new_type, new_rect, kTouchActionNone) {}
-
   DebugRectType type;
   gfx::Rect rect;
   // Valid when |type| is |TOUCH_EVENT_HANDLER_RECT_TYPE|, otherwise default to
   // |kTouchActionNone|.
   TouchAction touch_action;
+  // Valid when |type| is |MAIN_THREAD_SCROLLING_REASON_RECT_TYPE|, otherwise 0.
+  uint32_t main_thread_scrolling_reasons;
 };
 
 // This class maintains a history of rects of various types that can be used
@@ -105,6 +111,7 @@ class DebugRectHistory {
   void SaveScrollEventHandlerRectsCallback(LayerImpl* layer);
   void SaveNonFastScrollableRects(LayerTreeImpl* layer);
   void SaveNonFastScrollableRectsCallback(LayerImpl* layer);
+  void SaveMainThreadScrollingReasonRects(LayerTreeImpl*);
 
   std::vector<DebugRect> debug_rects_;
 };

content/renderer/render_widget.cc

@@ -1422,6 +1422,7 @@ void RenderWidget::SetShowScrollBottleneckRects(bool show) {
   debug_state.show_touch_event_handler_rects = show;
   debug_state.show_wheel_event_handler_rects = show;
   debug_state.show_non_fast_scrollable_rects = show;
+  debug_state.show_main_thread_scrolling_reason_rects = show;
   layer_tree_host_->SetDebugState(debug_state);
 }