[android_webview] Use a fraction to calculate scroll offset.

content/public/browser/android/synchronous_compositor_client.h

Index: content/public/browser/android/synchronous_compositor_client.h
diff --git a/content/public/browser/android/synchronous_compositor_client.h b/content/public/browser/android/synchronous_compositor_client.h
index bfd647b931dc9b7db0052f42aa30f1a624e87740..94ba28ffecfe8f12c11887f2fc6fd68bfb7dbf6d 100644
--- a/content/public/browser/android/synchronous_compositor_client.h
+++ b/content/public/browser/android/synchronous_compositor_client.h
@@ -25,8 +25,13 @@ class SynchronousCompositorClient {
   virtual void DidDestroyCompositor(SynchronousCompositor* compositor) = 0;
 
   // See LayerScrollOffsetDelegate for details.
+  virtual void SetMaxRootLayerScrollOffset(
+      gfx::Vector2dF max_scroll_offset) = 0;
   virtual void SetTotalRootLayerScrollOffset(gfx::Vector2dF new_value) = 0;
   virtual gfx::Vector2dF GetTotalRootLayerScrollOffset() = 0;
+  virtual void SetRootLayerPageScaleFactor(float page_scale_factor) = 0;
+  virtual void SetRootLayerScrollableSize(gfx::SizeF scrollable_size) = 0;
+
   virtual void DidOverscroll(gfx::Vector2dF accumulated_overscroll,
                              gfx::Vector2dF latest_overscroll_delta,
                              gfx::Vector2dF current_fling_velocity) = 0;