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

ui/android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java

Index: ui/android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java
diff --git a/ui/android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java b/ui/android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java
index 088c9c2476e7f2781572be7a56e1482965716dd3..84501daa2594f3b2f385f81caf82c1a8056de277 100644
--- a/ui/android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java
+++ b/ui/android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java
@@ -5,6 +5,8 @@
 package org.chromium.ui.gfx;
 
 import android.content.Context;
+import android.content.ComponentCallbacks;
+import android.content.res.Configuration;
 import android.graphics.PixelFormat;
 import android.os.Build;
 import android.util.DisplayMetrics;
@@ -115,6 +117,25 @@ public class DeviceDisplayInfo {
       return getMetrics().density;
   }
 
+  public void registerListener() {

[Yaron, 2013/10/11 10:18:14]

private

+      mAppContext.registerComponentCallbacks(
+          new ComponentCallbacks() {
+              @Override
+              public void onConfigurationChanged(Configuration configuration) {
+                updateNativeSharedDisplayInfo();

[Yaron, 2013/10/11 10:18:14]

indent 4 for block-level (other places below too). Please also correct the C++
code

+              }
+
+              @Override
+              public void onLowMemory() {
+              }
+      });
+  }
+
+  private void updateNativeSharedDisplayInfo() {
+    nativeUpdateSharedDeviceDisplayInfo(getDisplayHeight(), getDisplayWidth(),
+      getBitsPerPixel(), getBitsPerComponent(), getDIPScale());
+  }
+
   private Display getDisplay() {
       return mWinManager.getDefaultDisplay();
   }
@@ -128,8 +149,19 @@ public class DeviceDisplayInfo {
    * @param context A context to use.
    * @return DeviceDisplayInfo associated with a given Context.
    */
-  @CalledByNative
   public static DeviceDisplayInfo create(Context context) {
       return new DeviceDisplayInfo(context);
   }
+
+  @CalledByNative
+  public static DeviceDisplayInfo createWithListener(Context context) {

[Yaron, 2013/10/11 10:18:14]

Make private. This is unneeded from the java layer

+      DeviceDisplayInfo deviceDisplayInfo = new DeviceDisplayInfo(context);
+      deviceDisplayInfo.registerListener();
+      return deviceDisplayInfo;
+  }
+
+  private native void nativeUpdateSharedDeviceDisplayInfo(int displayHeight,
+                        int displayWidth, int bitsPerPixel,
+                        int bitsPerComponent, double dipScale);
+
 }