Remove dip scale dependency from ui::WindowAndroid

Starting from Android N dip scale can be changed dynamically.
In this CL we remove the dip scale impliciltly stored in
WindowAndroid's |content_offset_| and use the scale at the
time of calculations that involve the content offset.

This is a prerequisite for https://codereview.chromium.org/2202123002/

BUG=620929

Review-Url: https://codereview.chromium.org/2249243002
Cr-Commit-Position: refs/heads/master@{#412653}

content/browser/android/content_view_core_impl.cc

@@ -427,8 +427,7 @@ void ContentViewCoreImpl::UpdateFrameInfo(
   if (obj.is_null() || !view_.GetWindowAndroid())
     return;
 
-  view_.GetWindowAndroid()->set_content_offset(
-      gfx::ScaleVector2d(content_offset, dpi_scale_));
+  view_.GetWindowAndroid()->set_content_offset(content_offset);
 
   page_scale_ = page_scale_factor;
 

ui/android/view_android.cc

@@ -126,8 +126,8 @@ void ViewAndroid::SetAnchorRect(const JavaRef<jobject>& anchor,
   int left_margin = std::round(bounds.x() * scale);
   // TODO(jinsukkim): Move content_offset() to ViewAndroid, since it's
   //                  specific to a given web contents/render widget.
-  float content_offset_y_pix = GetWindowAndroid()->content_offset().y();
-  int top_margin = std::round(content_offset_y_pix + bounds.y() * scale);
+  int top_margin = std::round(
+      (GetWindowAndroid()->content_offset().y() + bounds.y()) * scale);
   JNIEnv* env = base::android::AttachCurrentThread();
   Java_ViewAndroidDelegate_setViewPosition(
       env, delegate, anchor, bounds.x(), bounds.y(), bounds.width(),

ui/android/window_android.h

@@ -35,8 +35,8 @@ class UI_ANDROID_EXPORT WindowAndroid : public ViewAndroid {
 
   static bool RegisterWindowAndroid(JNIEnv* env);
 
-  // The content offset is used to translate snapshots to the correct part of
-  // the window.
+  // The content offset in CSS pixels. It is used together with device scale
+  // factor to translate snapshots to the correct part of the window.
   void set_content_offset(const gfx::Vector2dF& content_offset) {
     content_offset_ = content_offset;
   }

ui/snapshot/snapshot_android.cc

@@ -49,10 +49,12 @@ static void MakeAsyncCopyRequest(
       gfx::ScaleToEnclosingRect(source_rect, device_scale_factor);
 
   // Account for the toolbar offset.
-  gfx::Vector2dF offset = window->content_offset();
-  gfx::Rect adjusted_source_rect(gfx::ToRoundedPoint(
-      gfx::PointF(source_rect_in_pixel.x() + offset.x(),
-                  source_rect_in_pixel.y() + offset.y())),
+  gfx::Vector2dF offset_in_pixel =
+      gfx::ScaleVector2d(window->content_offset(), device_scale_factor);
+  gfx::Rect adjusted_source_rect(
+      gfx::ToRoundedPoint(
+          gfx::PointF(source_rect_in_pixel.x() + offset_in_pixel.x(),
+                      source_rect_in_pixel.y() + offset_in_pixel.y())),
       source_rect_in_pixel.size());
 
   request->set_area(adjusted_source_rect);