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..1a460b060d0a92e60d01e20d7e4f31be39f2baa3 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;
@@ -36,7 +38,6 @@ public class DeviceDisplayInfo {
   /**
    * @return Display height in physical pixels.
    */
-  @CalledByNative
   public int getDisplayHeight() {
       return getMetrics().heightPixels;
   }
@@ -44,7 +45,6 @@ public class DeviceDisplayInfo {
   /**
    * @return Display width in physical pixels.
    */
-  @CalledByNative
   public int getDisplayWidth() {
       return getMetrics().widthPixels;
   }
@@ -61,7 +61,6 @@ public class DeviceDisplayInfo {
   /**
    * @return Bits per pixel.
    */
-  @CalledByNative
   public int getBitsPerPixel() {
       int format = getPixelFormat();
       PixelFormat info = new PixelFormat();
@@ -73,7 +72,6 @@ public class DeviceDisplayInfo {
    * @return Bits per component.
    */
   @SuppressWarnings("deprecation")
-  @CalledByNative
   public int getBitsPerComponent() {
       int format = getPixelFormat();
       switch (format) {
@@ -110,11 +108,31 @@ public class DeviceDisplayInfo {
    * @return A scaling factor for the Density Independent Pixel unit.
    *         1.0 is 160dpi, 0.75 is 120dpi, 2.0 is 320dpi.
    */
-  @CalledByNative
   public double getDIPScale() {
       return getMetrics().density;
   }
 
+  @CalledByNative
+  public void registerListener() {
+    mAppContext.registerComponentCallbacks(

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

nit: indent 4 (also below)

+        new ComponentCallbacks() {
+          @Override
+          public void onConfigurationChanged(Configuration configuration) {
+            updateNativeSharedDisplayInfo();
+          }

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

nit: add linebreak below

+          @Override
+          public void onLowMemory() {
+          }
+        });
+
+    updateNativeSharedDisplayInfo();
+  }
+
+  private void updateNativeSharedDisplayInfo() {
+     nativeUpdateSharedDisplayInfo(getDisplayHeight(), getDisplayWidth(),
+        getBitsPerPixel(), getBitsPerComponent(), getDIPScale());
+  }
+
   private Display getDisplay() {
       return mWinManager.getDefaultDisplay();
   }
@@ -123,6 +141,7 @@ public class DeviceDisplayInfo {
       return mAppContext.getResources().getDisplayMetrics();
   }
 
+
   /**
    * Creates DeviceDisplayInfo for a given Context.
    * @param context A context to use.
@@ -132,4 +151,9 @@ public class DeviceDisplayInfo {
   public static DeviceDisplayInfo create(Context context) {
       return new DeviceDisplayInfo(context);
   }
+
+  private native void nativeUpdateSharedDisplayInfo(int display_height,

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

java style should be displayHeight. Please update this and other variables

+                        int display_width, int bits_per_pixel,
+                        int bits_per_component, double dip_scale);
+
 }