webview: Initialize synchronous compositor after first activation.

content/browser/android/in_process/synchronous_compositor_impl.cc

Index: content/browser/android/in_process/synchronous_compositor_impl.cc
diff --git a/content/browser/android/in_process/synchronous_compositor_impl.cc b/content/browser/android/in_process/synchronous_compositor_impl.cc
index d3c6b830b7082bf6e2dec32f803b6751d249aa47..a44ccfe2b03925a14a1b45c5e10218fd7c9b17e0 100644
--- a/content/browser/android/in_process/synchronous_compositor_impl.cc
+++ b/content/browser/android/in_process/synchronous_compositor_impl.cc
@@ -74,6 +74,7 @@ SynchronousCompositorImpl::SynchronousCompositorImpl(WebContents* contents)
       contents_(contents),
       routing_id_(contents->GetRoutingID()),
       input_handler_(NULL),
+      registered_with_client_(false),
       is_active_(false),
       renderer_needs_begin_frames_(false),
       weak_ptr_factory_(this) {
@@ -108,6 +109,17 @@ void SynchronousCompositorImpl::SetClient(
   }
 }
 
+void SynchronousCompositorImpl::RegisterWithClient() {
+  DCHECK(CalledOnValidThread());
+
+  if (registered_with_client_)
+    return;
+
+  SetIsActive(false);
+  compositor_client_->DidInitializeCompositor(this);
+  registered_with_client_ = true;
+}
+
 // static
 void SynchronousCompositor::SetGpuService(
     scoped_refptr<gpu::InProcessCommandBuffer::Service> service) {
@@ -140,11 +152,10 @@ void SynchronousCompositorImpl::DidInitializeRendererObjects(
       base::Bind(&SynchronousCompositorImpl::DidActivatePendingTree,
                  weak_ptr_factory_.GetWeakPtr()));
 
-  OnNeedsBeginFramesChange(begin_frame_source_->NeedsBeginFrames());
-
-  compositor_client_->DidInitializeCompositor(this);
-
   SetInputHandler(input_handler);
+
+  OnNeedsBeginFramesChange(begin_frame_source_->NeedsBeginFrames());
+  SetIsActive(true);
 }
 
 void SynchronousCompositorImpl::DidDestroyRendererObjects() {
@@ -152,10 +163,17 @@ void SynchronousCompositorImpl::DidDestroyRendererObjects() {
   DCHECK(begin_frame_source_);
   DCHECK(compositor_client_);
 
+  if (registered_with_client_) {
+    compositor_client_->DidDestroyCompositor(this);
+    registered_with_client_ = false;
+  }
+
+  SetIsActive(false);
+  OnNeedsBeginFramesChange(false);
+
+  SetInputHandler(nullptr);
   begin_frame_source_->SetCompositor(nullptr);
   output_surface_->SetCompositor(nullptr);
-  SetInputHandler(nullptr);
-  compositor_client_->DidDestroyCompositor(this);
   output_surface_ = nullptr;
   begin_frame_source_ = nullptr;
 }
@@ -233,7 +251,8 @@ void SynchronousCompositorImpl::SetMemoryPolicy(size_t bytes_limit) {
 void SynchronousCompositorImpl::PostInvalidate() {
   DCHECK(CalledOnValidThread());
   DCHECK(compositor_client_);
-  compositor_client_->PostInvalidate();
+  if (registered_with_client_)
+    compositor_client_->PostInvalidate();
 }
 
 void SynchronousCompositorImpl::DidChangeRootLayerScrollOffset() {
@@ -282,9 +301,10 @@ void SynchronousCompositorImpl::SetInputHandler(
 void SynchronousCompositorImpl::DidOverscroll(
     const DidOverscrollParams& params) {
   DCHECK(compositor_client_);
-  compositor_client_->DidOverscroll(params.accumulated_overscroll,
-                                    params.latest_overscroll_delta,
-                                    params.current_fling_velocity);
+  if (registered_with_client_)
+    compositor_client_->DidOverscroll(params.accumulated_overscroll,
+                                      params.latest_overscroll_delta,
+                                      params.current_fling_velocity);
 }
 
 void SynchronousCompositorImpl::DidStopFlinging() {
@@ -315,6 +335,9 @@ void SynchronousCompositorImpl::DeliverMessages() {
 
 void SynchronousCompositorImpl::DidActivatePendingTree() {
   DCHECK(compositor_client_);
+  if (!registered_with_client_)
+    RegisterWithClient();
+  DCHECK(registered_with_client_);
   compositor_client_->DidUpdateContent();
   DeliverMessages();
 }
@@ -322,6 +345,8 @@ void SynchronousCompositorImpl::DidActivatePendingTree() {
 gfx::ScrollOffset SynchronousCompositorImpl::GetTotalScrollOffset() {
   DCHECK(CalledOnValidThread());
   DCHECK(compositor_client_);
+  if (!registered_with_client_)
+    return gfx::ScrollOffset();
   // TODO(miletus): Make GetTotalRootLayerScrollOffset return
   // ScrollOffset. crbug.com/414283.
   return gfx::ScrollOffset(
@@ -331,6 +356,8 @@ gfx::ScrollOffset SynchronousCompositorImpl::GetTotalScrollOffset() {
 bool SynchronousCompositorImpl::IsExternalFlingActive() const {
   DCHECK(CalledOnValidThread());
   DCHECK(compositor_client_);
+  if (!registered_with_client_)
+    return false;
   return compositor_client_->IsExternalFlingActive();
 }
 
@@ -344,14 +371,15 @@ void SynchronousCompositorImpl::UpdateRootLayerState(
   DCHECK(CalledOnValidThread());
   DCHECK(compositor_client_);
 
-  // TODO(miletus): Pass in ScrollOffset. crbug.com/414283.
-  compositor_client_->UpdateRootLayerState(
-      gfx::ScrollOffsetToVector2dF(total_scroll_offset),
-      gfx::ScrollOffsetToVector2dF(max_scroll_offset),
-      scrollable_size,
-      page_scale_factor,
-      min_page_scale_factor,
-      max_page_scale_factor);
+  if (registered_with_client_)

[boliu, 2015/05/30 01:06:29]

style: Need braces for if statements with multi-line body

+    // TODO(miletus): Pass in ScrollOffset. crbug.com/414283.
+    compositor_client_->UpdateRootLayerState(
+        gfx::ScrollOffsetToVector2dF(total_scroll_offset),
+        gfx::ScrollOffsetToVector2dF(max_scroll_offset),
+        scrollable_size,
+        page_scale_factor,
+        min_page_scale_factor,
+        max_page_scale_factor);
 }
 
 // Not using base::NonThreadSafe as we want to enforce a more exacting threading