Add observers for DIP scale change.

content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
index d0c951da7c477f2ad72424b826e488c551975a40..3526498bf02f5304a2e1c34ea77f3ef23ce213e0 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
@@ -82,6 +82,7 @@ import org.chromium.content_public.browser.WebContents;
 import org.chromium.content_public.browser.WebContentsObserver;
 import org.chromium.device.gamepad.GamepadList;
 import org.chromium.ui.base.DeviceFormFactor;
+import org.chromium.ui.base.DisplayObserver;
 import org.chromium.ui.base.ViewAndroidDelegate;
 import org.chromium.ui.base.WindowAndroid;
 import org.chromium.ui.base.ime.TextInputType;
@@ -101,9 +102,9 @@ import java.util.Map;
  * being tied to the view system.
  */
 @JNINamespace("content")
-public class ContentViewCore implements AccessibilityStateChangeListener, ScreenOrientationObserver,
-                                        SystemCaptioningBridge.SystemCaptioningBridgeListener,
-                                        WindowAndroidProvider {
+public class ContentViewCore
+        implements AccessibilityStateChangeListener, ScreenOrientationObserver, DisplayObserver,
+                   SystemCaptioningBridge.SystemCaptioningBridgeListener, WindowAndroidProvider {
     private static final String TAG = "cr_ContentViewCore";
 
     // Used to avoid enabling zooming in / out if resulting zooming will
@@ -659,7 +660,7 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
         setContainerViewInternals(internalDispatcher);
 
         mRenderCoordinates.reset();
-        mRenderCoordinates.setDeviceScaleFactor(getDisplayContext(windowAndroid));
+        onDIPScaleChanged(windowAndroid.getDIPScale());
 
         initPopupZoomer(mContext);
         mImeAdapter = createImeAdapter();
@@ -674,6 +675,9 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
      * @param windowAndroid The new {@link WindowAndroid} for this {@link ContentViewCore}.
      */
     public void updateWindowAndroid(WindowAndroid windowAndroid) {
+        WindowAndroid oldWindowAndroid = getWindowAndroid();
+        if (oldWindowAndroid != null) oldWindowAndroid.removeDisplayObserver(this);
+
         long windowNativePointer = windowAndroid == null ? 0 : windowAndroid.getNativePointer();
         nativeUpdateWindowAndroid(mNativeContentViewCore, windowNativePointer);
 
@@ -682,7 +686,7 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
         mSelectPopup = null;
         mPastePopupMenu = null;
 
-        mRenderCoordinates.setDeviceScaleFactor(getDisplayContext(windowAndroid));
+        if (windowAndroid != null) windowAndroid.addDisplayObserver(this);
 
         for (WindowAndroidChangedObserver observer : mWindowAndroidChangedObservers) {
             observer.onWindowAndroidChanged(windowAndroid);
@@ -1361,6 +1365,11 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
         mAccessibilityManager.addAccessibilityStateChangeListener(this);
         mSystemCaptioningBridge.addListener(this);
         mImeAdapter.onViewAttachedToWindow();
+
+        WindowAndroid windowAndroid = getWindowAndroid();
+        if (windowAndroid != null) {
+            windowAndroid.addDisplayObserver(this);
+        }
     }
 
     /**
@@ -1386,6 +1395,11 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
     @SuppressWarnings("javadoc")
     @SuppressLint("MissingSuperCall")
     public void onDetachedFromWindow() {
+        WindowAndroid windowAndroid = getWindowAndroid();
+        if (windowAndroid != null) {
+            windowAndroid.removeDisplayObserver(this);
+        }
+
         mImeAdapter.onViewDetachedFromWindow();
         mZoomControlsDelegate.dismissZoomPicker();
 
@@ -3246,6 +3260,15 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
         sendOrientationChangeEvent(orientation);
     }
 
+    // DisplayObserver method implementation.
+    @Override
+    public void onDIPScaleChanged(float dipScale) {
+        if (mNativeContentViewCore == 0) return;
+        nativeSetDIPScale(mNativeContentViewCore, dipScale);
+
+        mRenderCoordinates.setDeviceScaleFactor(dipScale, getDisplayContext(getWindowAndroid()));
+    }
+
     /**
      * Set whether the ContentViewCore requires the WebContents to be fullscreen in order to lock
      * the screen orientation.
@@ -3310,6 +3333,8 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
 
     private native void nativeSetFocus(long nativeContentViewCoreImpl, boolean focused);
 
+    private native void nativeSetDIPScale(long nativeContentViewCoreImpl, float dipScale);
+
     private native void nativeSendOrientationChangeEvent(
             long nativeContentViewCoreImpl, int orientation);