[android_webview] Use a fraction to calculate scroll offset.

android_webview/browser/in_process_view_renderer.h

 // 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.
 
 #ifndef ANDROID_WEBVIEW_BROWSER_IN_PROCESS_VIEW_RENDERER_H_
 #define ANDROID_WEBVIEW_BROWSER_IN_PROCESS_VIEW_RENDERER_H_
 
 #include <string>
 
 #include "android_webview/browser/browser_view_renderer.h"
@@ skipping 61 matching lines @@
   virtual bool IsAttachedToWindow() OVERRIDE;
   virtual bool IsVisible() OVERRIDE;
   virtual gfx::Rect GetScreenRect() OVERRIDE;
 
   // SynchronousCompositorClient overrides
   virtual void DidInitializeCompositor(
       content::SynchronousCompositor* compositor) OVERRIDE;
   virtual void DidDestroyCompositor(
       content::SynchronousCompositor* compositor) OVERRIDE;
   virtual void SetContinuousInvalidate(bool invalidate) OVERRIDE;
+  virtual void SetMaxRootLayerScrollOffset(gfx::Vector2dF new_value) OVERRIDE;
   virtual void SetTotalRootLayerScrollOffset(
       gfx::Vector2dF new_value_css) OVERRIDE;
   virtual void DidUpdateContent() OVERRIDE;
   virtual gfx::Vector2dF GetTotalRootLayerScrollOffset() OVERRIDE;
   virtual void DidOverscroll(gfx::Vector2dF accumulated_overscroll,
                              gfx::Vector2dF latest_overscroll_delta,
                              gfx::Vector2dF current_fling_velocity) OVERRIDE;
 
   void WebContentsGone();
   bool RequestProcessGL();
@@ skipping 12 matching lines @@
   void UpdateCachedGlobalVisibleRect();
 
   // If we call up view invalidate and OnDraw is not called before a deadline,
   // then we keep ticking the SynchronousCompositor so it can make progress.
   void FallbackTickFired();
 
   void NoLongerExpectsDrawGL();
 
   bool InitializeHwDraw();
 
+  gfx::Vector2d max_scroll_offset() const;
+
   // For debug tracing or logging. Return the string representation of this
   // view renderer's state and the |draw_info| if provided.
   std::string ToString(AwDrawGLInfo* draw_info) const;
 
   BrowserViewRenderer::Client* client_;
   BrowserViewRenderer::JavaHelper* java_helper_;
   content::WebContents* web_contents_;
   content::SynchronousCompositor* compositor_;
 
   bool is_paused_;
@@ skipping 29 matching lines @@
   // Not to be used between draw calls.
   EGLContext last_egl_context_;
 
   // Should always call UpdateCachedGlobalVisibleRect before using this.
   gfx::Rect cached_global_visible_rect_;
 
   // Last View scroll when View.onDraw() was called.
   gfx::Vector2d scroll_at_start_of_frame_;
 
   // Current scroll offset in CSS pixels.
-  gfx::Vector2dF scroll_offset_css_;
+  gfx::Vector2dF scroll_offset_dip_;
+
+  // Max scroll offset in CSS pixels.
+  gfx::Vector2dF max_scroll_offset_dip_;
 
   // Used to prevent rounding errors from accumulating enough to generate
   // visible skew (especially noticeable when scrolling up and down in the same
   // spot over a period of time).
   gfx::Vector2dF overscroll_rounding_error_;
 
   GLViewRendererManager::Key manager_key_;
 
   DISALLOW_COPY_AND_ASSIGN(InProcessViewRenderer);
 };
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_BROWSER_IN_PROCESS_VIEW_RENDERER_H_