gpu: Draw quad debug borders with different colors.

Change color of drawquad debug borders based on x-scaling to make
it easier to distinguish neighbouring quads.

BUG=
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2670793004
Cr-Commit-Position: refs/heads/master@{#448364}

cc/debug/debug_colors.cc

@@ -138,6 +138,19 @@ int DebugColors::DirectPictureBorderWidth(const LayerTreeImpl* tree_impl) {
   return Scale(1, tree_impl);
 }
 
+// Borders added to GL composited draw quads. This is useful to debug HW
+// overlays. When the border disappears, it means we're using an overlay.
+// We draw borders in different colors to be able to distinguish neighboring
+// quads (often shadows).
+SkColor DebugColors::GLCompositedTextureQuadBorderColor(int index) {
+  const SkColor kColors[] = {SK_ColorBLUE,   SK_ColorGREEN, SK_ColorRED,
+                             SK_ColorYELLOW, SK_ColorCYAN,  SK_ColorMAGENTA};
+  return kColors[index % arraysize(kColors)];
+}
+int DebugColors::GLCompositedTextureQuadBoderWidth() {
+  return 6;
+}
+
 // Compressed tile borders are blue.
 SkColor DebugColors::CompressedTileBorderColor() {
   return SkColorSetARGB(100, 20, 20, 240);

cc/debug/debug_colors.h

@@ -108,6 +108,9 @@ class DebugColors {
   static SkColor MissingResizeInvalidations();
   static SkColor PictureBorderColor();
 
+  static SkColor GLCompositedTextureQuadBorderColor(int index);
+  static int GLCompositedTextureQuadBoderWidth();
+
   static SkColor HUDBackgroundColor();
   static SkColor HUDSeparatorLineColor();
   static SkColor HUDIndicatorLineColor();

cc/output/gl_renderer.cc

@@ -27,6 +27,7 @@
 #include "build/build_config.h"
 #include "cc/base/container_util.h"
 #include "cc/base/math_util.h"
+#include "cc/debug/debug_colors.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_metadata.h"
 #include "cc/output/context_provider.h"
@@ -2428,9 +2429,15 @@ void GLRenderer::FlushTextureQuadCache(BoundGeometry flush_binding) {
         program->matrix_location(), 1, false,
         reinterpret_cast<float*>(&draw_cache_.matrix_data.front()));
 
-    gl_->Uniform4f(program->color_location(), 0.0f, 1.0f, 0.0f, 1.0f);
+    // Pick a random color based on the scale on X and Y.
+    int colorIndex = static_cast<int>(draw_cache_.matrix_data.front().data[0] *
+                                      draw_cache_.matrix_data.front().data[5]);
+    SkColor color = DebugColors::GLCompositedTextureQuadBorderColor(colorIndex);
 
-    gl_->LineWidth(3.0f);
+    gl_->Uniform4f(program->color_location(), SkColorGetR(color),
+                   SkColorGetG(color), SkColorGetB(color), 1.0f);
+
+    gl_->LineWidth(DebugColors::GLCompositedTextureQuadBoderWidth());
     // The indices for the line are stored in the same array as the triangle
     // indices.
     gl_->DrawElements(GL_LINE_LOOP, 4, GL_UNSIGNED_SHORT, 0);