cc: Use max_bytes_per_copy_operation setting to determine one-copy flush interval.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index abc113929c2b8f9cf38e7b7c8bca0e7330b3ffd8..273a5c95eac349729af70a6d0bd17fc2f92ab8ef 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -178,6 +178,14 @@ gfx::Size CalculateDefaultTileSize(RenderWidget* widget) {
   return gfx::Size(default_tile_size, default_tile_size);
 }
 
+int GetMaxBytesPerCopyOperation() {
+  const int kMegabyte = 1024 * 1024;
+
+  // 4MiB is the size of 4 512x512 tiles, which has proven to be a good
+  // default batch size for copy operations.
+  return kMegabyte * 4;
+}
+
 // Check cc::TopControlsState, and blink::WebTopControlsState
 // are kept in sync.
 static_assert(int(blink::WebTopControlsBoth) == int(cc::BOTH),
@@ -456,6 +464,8 @@ void RenderWidgetCompositor::Initialize() {
     settings.use_external_begin_frame_source = false;
   }
 
+  settings.max_bytes_per_copy_operation = GetMaxBytesPerCopyOperation();
+
   scoped_refptr<base::SingleThreadTaskRunner> compositor_thread_task_runner =
       compositor_deps_->GetCompositorImplThreadTaskRunner();
   scoped_refptr<base::SingleThreadTaskRunner>