Delegate root layer scroll offset to android_webview.

content/renderer/android/synchronous_compositor_impl.cc

Index: content/renderer/android/synchronous_compositor_impl.cc
diff --git a/content/renderer/android/synchronous_compositor_impl.cc b/content/renderer/android/synchronous_compositor_impl.cc
index 5b54c27fe72e6fc3cb1a46900ee8049c9fb30716..7688ff300bd08dc34896cbbc2c3d2818903125a2 100644
--- a/content/renderer/android/synchronous_compositor_impl.cc
+++ b/content/renderer/android/synchronous_compositor_impl.cc
@@ -12,7 +12,8 @@
 namespace content {
 
 SynchronousCompositorImpl::SynchronousCompositorImpl(int32 routing_id)
-    : routing_id_(routing_id), compositor_client_(NULL) {}
+    : routing_id_(routing_id), compositor_client_(NULL) {
+}
 
 SynchronousCompositorImpl::~SynchronousCompositorImpl() {
 }
@@ -57,7 +58,6 @@ bool SynchronousCompositorImpl::DemandDrawHw(
 
 void SynchronousCompositorImpl::SetContinuousInvalidate(bool enable) {
   DCHECK(CalledOnValidThread());
-  // compositor_client_ can be NULL during WebContents teardown.
   if (compositor_client_)
     compositor_client_->SetContinuousInvalidate(enable);
 }
@@ -71,11 +71,24 @@ void SynchronousCompositorImpl::DidCreateSynchronousOutputSurface() {
 void SynchronousCompositorImpl::DidDestroySynchronousOutputSurface() {
   DCHECK(CalledOnValidThread());
   output_surface_ = NULL;
-  // compositor_client_ can be NULL during WebContents teardown.
   if (compositor_client_)
     compositor_client_->DidDestroyCompositor(this);
 }
 
+void SynchronousCompositorImpl::SetTotalScrollOffset(gfx::Vector2dF new_value) {
+  DCHECK(CalledOnValidThread());
+  if (compositor_client_)
+    compositor_client_->SetTotalRootLayerScrollOffset(new_value);
+}
+
+gfx::Vector2dF SynchronousCompositorImpl::GetTotalScrollOffset() {
+  DCHECK(CalledOnValidThread());
+  if (compositor_client_)
+    return compositor_client_->GetTotalRootLayerScrollOffset();
+  else
+    return gfx::Vector2dF();

[mkosiba (inactive), 2013/05/29 13:18:24]

this is the only downside of checking for compositor_client_ (instead of
removing the scroll offset delegate ). If the compositor_client_ can only be
NULL during setup/teardown then this is fine, but otherwise this could lead to
the page scroll jumping to the top at seemingly arbitrary times.

+}
+
 // Not using base::NonThreadSafe as we want to enforce a more exacting threading
 // requirement: SynchronousCompositorImpl() must only be used by
 // embedders that supply their own compositor loop via