[Android WebView] OnMemoryPressure to drop tile memory

android_webview/browser/in_process_view_renderer.h

Index: android_webview/browser/in_process_view_renderer.h
diff --git a/android_webview/browser/in_process_view_renderer.h b/android_webview/browser/in_process_view_renderer.h
index ce5c5841f6ad1d04249c4e10bfbf760abc4d875d..b074c35578ef8e6a57144f1bd24e677d1b91fcd2 100644
--- a/android_webview/browser/in_process_view_renderer.h
+++ b/android_webview/browser/in_process_view_renderer.h
@@ -10,6 +10,7 @@
 #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"
 
@@ -111,6 +112,9 @@ class InProcessViewRenderer : public BrowserViewRenderer,
 
   void NoLongerExpectsDrawGL();
 
+  void OnMemoryPressure(
+      base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
+
   bool InitializeHwDraw();
 
   gfx::Vector2d max_scroll_offset() const;
@@ -176,6 +180,8 @@ class InProcessViewRenderer : public BrowserViewRenderer,
 
   GLViewRendererManager::Key manager_key_;
 
+  scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(InProcessViewRenderer);
 };