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..9454df92a85557134cc50ba1adb0b7765cdf9b33 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));
@@ -167,7 +169,17 @@ void SurfacesInstance::RemoveChildId(const cc::SurfaceId& child_id) {
 }
 
 void SurfacesInstance::SetEmptyRootFrame() {

[boliu, 2017/05/04 17:08:00]

rename the method name and variable names please, since it's no longer empty.
should reflect that this sets a frame that does not refer to any other surface
ids

[Saman Sami, 2017/05/04 21:38:46]

Done.

+  if (!root_id_.is_valid())

[boliu, 2017/05/04 17:08:00]

this should be a DCHECK it looks like? every call to this method already have
this check

[Saman Sami, 2017/05/04 21:38:46]

Done.

+    return;
+  std::unique_ptr<cc::RenderPass> render_pass = cc::RenderPass::Create();
+  cc::SharedQuadState* quad_state =
+      render_pass->CreateAndAppendSharedQuadState();
+  gfx::Rect rect(surface_size_);
+  cc::SolidColorDrawQuad* solid_quad =
+      render_pass->CreateAndAppendDrawQuad<cc::SolidColorDrawQuad>();
+  solid_quad->SetNew(quad_state, rect, rect, SK_ColorBLACK, false);
   cc::CompositorFrame empty_frame;
+  empty_frame.render_pass_list.push_back(std::move(render_pass));
   // We draw synchronously, so acknowledge a manual BeginFrame.
   empty_frame.metadata.begin_frame_ack =
       cc::BeginFrameAck::CreateManualAckWithDamage();