[android_webview] Use a fraction to calculate scroll offset.

content/browser/android/in_process/synchronous_compositor_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/android/in_process/synchronous_compositor_impl.h"
 
 #include "base/lazy_instance.h"
 #include "base/message_loop/message_loop.h"
 #include "base/synchronization/lock.h"
 #include "cc/input/input_handler.h"
@@ skipping 397 matching lines @@
       contents_->GetRenderWidgetHostView());
   if (rwhv)
     rwhv->SynchronousFrameMetadata(frame_metadata);
 }
 
 void SynchronousCompositorImpl::DidActivatePendingTree() {
   if (compositor_client_)
     compositor_client_->DidUpdateContent();
 }
 
+void SynchronousCompositorImpl::SetMaxScrollOffset(
+    gfx::Vector2dF max_scroll_offset) {
+  DCHECK(CalledOnValidThread());
+  if (compositor_client_)
+    compositor_client_->SetMaxRootLayerScrollOffset(max_scroll_offset);
+}
+
 void SynchronousCompositorImpl::SetTotalScrollOffset(gfx::Vector2dF new_value) {
   DCHECK(CalledOnValidThread());
-  if (compositor_client_)
+  if (compositor_client_) {
     compositor_client_->SetTotalRootLayerScrollOffset(new_value);
+  }
 }
 
 gfx::Vector2dF SynchronousCompositorImpl::GetTotalScrollOffset() {
   DCHECK(CalledOnValidThread());
   if (compositor_client_)
     return compositor_client_->GetTotalRootLayerScrollOffset();
   return gfx::Vector2dF();
 }
 
 // Not using base::NonThreadSafe as we want to enforce a more exacting threading
@@ skipping 11 matching lines @@
     g_factory.Get();  // Ensure it's initialized.
     SynchronousCompositorImpl::CreateForWebContents(contents);
   }
   if (SynchronousCompositorImpl* instance =
       SynchronousCompositorImpl::FromWebContents(contents)) {
     instance->SetClient(client);
   }
 }
 
 }  // namespace content