Don't submit empty frames in android webview

android_webview/browser/surfaces_instance.cc

Index: android_webview/browser/surfaces_instance.cc
diff --git a/android_webview/browser/surfaces_instance.cc b/android_webview/browser/surfaces_instance.cc
index c09e9a606a40e7ba6b58e7fc0cb85493660dd18f..b8599fe91175b5e7f1707cb68f7d8cf789bf212a 100644
--- a/android_webview/browser/surfaces_instance.cc
+++ b/android_webview/browser/surfaces_instance.cc
@@ -14,6 +14,7 @@
 #include "base/memory/ptr_util.h"
 #include "cc/output/renderer_settings.h"
 #include "cc/output/texture_mailbox_deleter.h"
+#include "cc/quads/solid_color_draw_quad.h"
 #include "cc/quads/surface_draw_quad.h"
 #include "cc/scheduler/begin_frame_source.h"
 #include "cc/surfaces/compositor_frame_sink_support.h"
@@ -140,8 +141,9 @@ void SurfacesInstance::DrawAndSwap(const gfx::Size& viewport,
   frame.render_pass_list.push_back(std::move(render_pass));
   frame.metadata.referenced_surfaces = child_ids_;
 
-  if (!root_id_.is_valid()) {
+  if (!root_id_.is_valid() || frame_size != surface_size_) {
     root_id_ = local_surface_id_allocator_->GenerateId();
+    surface_size_ = frame_size;
     display_->SetLocalSurfaceId(root_id_, 1.f);
   }
   support_->SubmitCompositorFrame(root_id_, std::move(frame));
@@ -155,7 +157,7 @@ void SurfacesInstance::AddChildId(const cc::SurfaceId& child_id) {
          child_ids_.end());
   child_ids_.push_back(child_id);
   if (root_id_.is_valid())
-    SetEmptyRootFrame();
+    SetSolidColorRootFrame();
 }
 
 void SurfacesInstance::RemoveChildId(const cc::SurfaceId& child_id) {
@@ -163,16 +165,28 @@ void SurfacesInstance::RemoveChildId(const cc::SurfaceId& child_id) {
   DCHECK(itr != child_ids_.end());
   child_ids_.erase(itr);
   if (root_id_.is_valid())
-    SetEmptyRootFrame();
+    SetSolidColorRootFrame();
 }
 
-void SurfacesInstance::SetEmptyRootFrame() {
-  cc::CompositorFrame empty_frame;
+void SurfacesInstance::SetSolidColorRootFrame() {
+  DCHECK(!surface_size_.IsEmpty());
+  gfx::Rect rect(surface_size_);
+  std::unique_ptr<cc::RenderPass> render_pass = cc::RenderPass::Create();
+  render_pass->SetNew(1, rect, rect, gfx::Transform());
+  cc::SharedQuadState* quad_state =
+      render_pass->CreateAndAppendSharedQuadState();
+  quad_state->SetAll(gfx::Transform(), rect, rect, rect, false, 1.f,
+                     SkBlendMode::kSrcOver, 0);
+  cc::SolidColorDrawQuad* solid_quad =
+      render_pass->CreateAndAppendDrawQuad<cc::SolidColorDrawQuad>();
+  solid_quad->SetNew(quad_state, rect, rect, SK_ColorBLACK, false);
+  cc::CompositorFrame frame;
+  frame.render_pass_list.push_back(std::move(render_pass));
   // We draw synchronously, so acknowledge a manual BeginFrame.
-  empty_frame.metadata.begin_frame_ack =
+  frame.metadata.begin_frame_ack =
       cc::BeginFrameAck::CreateManualAckWithDamage();
-  empty_frame.metadata.referenced_surfaces = child_ids_;
-  support_->SubmitCompositorFrame(root_id_, std::move(empty_frame));
+  frame.metadata.referenced_surfaces = child_ids_;
+  support_->SubmitCompositorFrame(root_id_, std::move(frame));
 }
 
 void SurfacesInstance::DidReceiveCompositorFrameAck(