Cache DeviceDisplayInfo data in shared structure on native side to avoid frequent JNI calls.

ui/gfx/android/device_display_info.h

 // Copyright (c) 2012 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 UI_GFX_ANDROID_DEVICE_DISPLAY_INFO_H_
 #define UI_GFX_ANDROID_DEVICE_DISPLAY_INFO_H_
 
 #include <jni.h>
 #include <string>
 
 #include "base/android/scoped_java_ref.h"
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"

[Yaron, 2013/10/10 11:52:46]

You'll be able to remove by changing to LazyInstance in just the cc file

 #include "ui/gfx/gfx_export.h"
 
 namespace gfx {
 
 // Facilitates access to device information typically only
 // available using the Android SDK, including Display properties.
 class GFX_EXPORT DeviceDisplayInfo {
  public:
   DeviceDisplayInfo();
   ~DeviceDisplayInfo();
 
   // Returns display height in physical pixels.
   int GetDisplayHeight();
 
   // Returns display width in physical pixels.
   int GetDisplayWidth();
 
   // Returns number of bits per pixel.
   int GetBitsPerPixel();
 
   // Returns number of bits per component.
   int GetBitsPerComponent();
 
   // Returns a scaling factor for Density Independent Pixel unit
   // (1.0 is 160dpi, 0.75 is 120dpi, 2.0 is 320dpi).
   double GetDIPScale();
 
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DeviceDisplayInfo);
+};
+
+class GFX_EXPORT SharedDisplayInfo {
+ public:
+  static int GetDisplayHeight();
+  static int GetDisplayWidth();
+  static int GetBitsPerPixel();
+  static int GetBitsPerComponent();
+  static double GetDIPScale();
+
+  static void UpdateDisplayInfo(JNIEnv*, jobject, jint display_height,
+        jint display_width, jint bits_per_pixel, jint bits_per_component,
+        jdouble dip_scale);
+
   // Registers methods with JNI and returns true if succeeded.
-  static bool RegisterDeviceDisplayInfo(JNIEnv* env);
+  static bool RegisterSharedDeviceDisplayInfo(JNIEnv* env);
 
  private:
+  static SharedDisplayInfo* Instance();
+  SharedDisplayInfo();
+
+  void InvokeUpdate();

[Yaron, 2013/10/10 11:52:46]

never called

+  void RegisterListener();
+
+  static scoped_ptr<SharedDisplayInfo> instance_;
+
   base::android::ScopedJavaGlobalRef<jobject> j_device_info_;
 
-  DISALLOW_COPY_AND_ASSIGN(DeviceDisplayInfo);
+  int display_height_;
+  int display_width_;
+  int bits_per_pixel_;
+  int bits_per_component_;
+  double dip_scale_;
 };
 
+
+
 }  // namespace gfx
 
 #endif  // UI_GFX_ANDROID_DEVICE_DISPLAY_INFO_H_