Turn off computation of the interest rect in cc in synchronized paint mode.

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 641946864ca300aa16117880873e619d7d43443a..9b498538a5eec4c392cfe29320f30bf650d08352 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -307,6 +307,9 @@ void RenderWidgetCompositor::Initialize() {
   settings.image_decode_tasks_enabled =
       compositor_deps_->AreImageDecodeTasksEnabled();
 
+  settings.blink_synchronized_painting_enabled =
+    cmd->HasSwitch(switches::kEnableBlinkSynchronizedPainting);
+
   if (cmd->HasSwitch(cc::switches::kTopControlsShowThreshold)) {
       std::string top_threshold_str =
           cmd->GetSwitchValueASCII(cc::switches::kTopControlsShowThreshold);