[android_webview] Use a fraction to calculate scroll offset.

cc/layers/layer_impl_unittest.cc

Index: cc/layers/layer_impl_unittest.cc
diff --git a/cc/layers/layer_impl_unittest.cc b/cc/layers/layer_impl_unittest.cc
index 1ab7a71b2ca93a2d39c3e66e1201fa7a88da65b2..e2b29df8d778751a9e62a24967273787b1c74e29 100644
--- a/cc/layers/layer_impl_unittest.cc
+++ b/cc/layers/layer_impl_unittest.cc
@@ -391,6 +391,7 @@ TEST_F(LayerImplScrollTest, ScrollByWithNonZeroOffset) {
 
 class ScrollDelegateIgnore : public LayerScrollOffsetDelegate {
  public:
+  virtual void SetMaxScrollOffset(gfx::Vector2dF max_scroll_offset) OVERRIDE {}
   virtual void SetTotalScrollOffset(gfx::Vector2dF new_value) OVERRIDE {}
   virtual gfx::Vector2dF GetTotalScrollOffset() OVERRIDE {
     return fixed_offset_;
@@ -400,6 +401,9 @@ class ScrollDelegateIgnore : public LayerScrollOffsetDelegate {
     fixed_offset_ = fixed_offset;
   }
 
+  virtual void SetPageScaleFactor(float page_scale_factor) OVERRIDE {}
+  virtual void SetScrollableSize(gfx::SizeF scrollable_size) OVERRIDE {}
+
  private:
   gfx::Vector2dF fixed_offset_;
 };
@@ -441,12 +445,15 @@ TEST_F(LayerImplScrollTest, ScrollByWithIgnoringDelegate) {
 
 class ScrollDelegateAccept : public LayerScrollOffsetDelegate {
  public:
+  virtual void SetMaxScrollOffset(gfx::Vector2dF max_scroll_offset) OVERRIDE {}
   virtual void SetTotalScrollOffset(gfx::Vector2dF new_value) OVERRIDE {
     current_offset_ = new_value;
   }
   virtual gfx::Vector2dF GetTotalScrollOffset() OVERRIDE {
     return current_offset_;
   }
+  virtual void SetPageScaleFactor(float page_scale_factor) OVERRIDE {}
+  virtual void SetScrollableSize(gfx::SizeF scrollable_size) OVERRIDE {}
 
  private:
   gfx::Vector2dF current_offset_;