[Android WebView] OnMemoryPressure to drop tile memory

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"
 #include "android_webview/browser/gl_view_renderer_manager.h"
 #include "base/cancelable_callback.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "content/public/browser/android/synchronous_compositor_client.h"
 #include "ui/gfx/vector2d_f.h"
 
 namespace content {
 class SynchronousCompositor;
 class WebContents;
 }
 
 typedef void* EGLContext;
 class SkCanvas;
@@ skipping 81 matching lines @@
   bool CompositeSW(SkCanvas* canvas);
 
   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();
 
+  void OnMemoryPressure(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
   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_;
@@ skipping 45 matching lines @@
   // 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_;
 
+  scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(InProcessViewRenderer);
 };
 
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_BROWSER_IN_PROCESS_VIEW_RENDERER_H_