[android_webview] Use a fraction to calculate scroll offset.

android_webview/browser/browser_view_renderer.h

 // Copyright (c) 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.
 
 #ifndef ANDROID_WEBVIEW_BROWSER_BROWSER_VIEW_RENDERER_H_
 #define ANDROID_WEBVIEW_BROWSER_BROWSER_VIEW_RENDERER_H_
 
 #include "base/android/scoped_java_ref.h"
 #include "skia/ext/refptr.h"
 #include "ui/gfx/point.h"
@@ skipping 30 matching lines @@
 
     // Synchronously call back to SetGlobalVisibleRect with current value.
     virtual void UpdateGlobalVisibleRect() = 0;
 
     // Called to get view's absolute location on the screen.
     virtual gfx::Point GetLocationOnScreen() = 0;
 
     // Try to set the view's scroll offset to |new_value|.
     virtual void ScrollContainerViewTo(gfx::Vector2d new_value) = 0;
 
+    // Set the view's scroll offset cap to |new_value|.
+    virtual void SetMaxContainerViewScrollOffset(gfx::Vector2d new_value) = 0;
+
     // Handle overscroll.
     virtual void DidOverscroll(gfx::Vector2d overscroll_delta) = 0;
 
    protected:
     virtual ~Client() {}
   };
 
   // Delegate to perform rendering actions involving Java objects.
   class JavaHelper {
    public:
@@ skipping 70 matching lines @@
   virtual bool IsAttachedToWindow() = 0;
   virtual bool IsVisible() = 0;
   virtual gfx::Rect GetScreenRect() = 0;
 
   virtual ~BrowserViewRenderer() {}
 };
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_BROWSER_BROWSER_VIEW_RENDERER_H_