Make WebView respond to device scale change

android_webview/java/src/org/chromium/android_webview/AwContents.java

Index: android_webview/java/src/org/chromium/android_webview/AwContents.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContents.java b/android_webview/java/src/org/chromium/android_webview/AwContents.java
index a3dbd95e3576653464aabdc50a83f32b418d5df6..4aad0c4ee6d0edb55b1313a2971d76c6ea819f4e 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -300,7 +300,7 @@ public class AwContents implements SmartClipProvider,
     private Bitmap mFavicon;
     private boolean mHasRequestedVisitedHistoryFromClient;
     // TODO(boliu): This should be in a global context, not per webview.
-    private final double mDIPScale;
+    private double mDIPScale;
     // Whether this WebView is a popup.
     private boolean mIsPopupWindow = false;
 
@@ -712,6 +712,16 @@ public class AwContents implements SmartClipProvider,
         public void onConfigurationChanged(Configuration configuration) {
             setLocale(LocaleUtils.getLocale(configuration.locale));
             mSettings.updateAcceptLanguages();
+
+            DeviceDisplayInfo displayInfo = DeviceDisplayInfo.create(mContext);
+            // Update all display related parameters.
+            displayInfo.updateNativeSharedDisplayInfo();
+
+            final double newDIPScale = displayInfo.getDIPScale();
+            if (newDIPScale != mDIPScale) {
+                mContentViewCore.setDeviceScaleFactor((float) newDIPScale);
+                setDIPScale(newDIPScale);
+            }
         }
     };
 
@@ -771,9 +781,7 @@ public class AwContents implements SmartClipProvider,
         mContentViewClient = new AwContentViewClient(contentsClient, settings, this, mContext);
         mLayoutSizer = dependencyFactory.createLayoutSizer();
         mSettings = settings;
-        mDIPScale = DeviceDisplayInfo.create(mContext).getDIPScale();
         mLayoutSizer.setDelegate(new AwLayoutSizerDelegate());
-        mLayoutSizer.setDIPScale(mDIPScale);
         mWebContentsDelegate = new AwWebContentsDelegateAdapter(
                 this, contentsClient, mContentViewClient, mContext, mContainerView);
         mContentsClientBridge = new AwContentsClientBridge(mContext, contentsClient,
@@ -804,7 +812,6 @@ public class AwContents implements SmartClipProvider,
         mDefaultVideoPosterRequestHandler = new DefaultVideoPosterRequestHandler(mContentsClient);
         mSettings.setDefaultVideoPosterURL(
                 mDefaultVideoPosterRequestHandler.getDefaultVideoPosterURL());
-        mSettings.setDIPScale(mDIPScale);
         mScrollOffsetManager =
                 dependencyFactory.createScrollOffsetManager(new AwScrollOffsetManagerDelegate());
         mScrollAccessibilityHelper = new ScrollAccessibilityHelper(mContainerView);
@@ -829,6 +836,13 @@ public class AwContents implements SmartClipProvider,
         contentViewCore.setZoomControlsDelegate(zoomControlsDelegate);
     }
 
+    private void setDIPScale(double dipScale) {
+        mDIPScale = dipScale;
+        nativeSetDipScale(mNativeAwContents, (float) mDIPScale);
+        mSettings.setDIPScale(mDIPScale);
+        mLayoutSizer.setDIPScale(mDIPScale);
+    }
+
     boolean isFullScreen() {
         return mFullScreenTransitionsState.isFullScreen();
     }
@@ -1061,7 +1075,10 @@ public class AwContents implements SmartClipProvider,
         mNavigationController = mWebContents.getNavigationController();
         installWebContentsObserver();
         mSettings.setWebContents(webContents);
-        nativeSetDipScale(mNativeAwContents, (float) mDIPScale);
+
+        // ContentViewCore requests and stores the device scale factor.
+        setDIPScale(mContentViewCore.getDeviceScaleFactor());
+
         updateContentViewCoreVisibility();
 
         // The native side object has been bound to this java instance, so now is the time to
@@ -3204,8 +3221,7 @@ public class AwContents implements SmartClipProvider,
             // to enter fixedLayoutSize mode is sent before the first resize
             // update.
             mLayoutSizer.onSizeChanged(w, h, ow, oh);
-            mContentViewCore.onPhysicalBackingSizeChanged(w, h);
-            mContentViewCore.onSizeChanged(w, h, ow, oh);
+            mContentViewCore.onPhysicalAndViewportSizeChanged(w, h);

[Tima Vaisburd, 2016/08/22 19:06:25]

I still did not understand why the second call does not work. I saw the first
call issued and extra blink::FrameView::layout() triggered by the style change
detection and this layout was missed on the second call, but this is not the
root cause.
During rotation we have the similar wrong size followed by the right size, but
in the case of rotation the first wrong size is same as the old one and it is
optimized away completely.
In the other places onPhysicalBackingSizeChanged() and onSizeChanged() do not
come together, the first one (as far as I get) is bound to the surface size
change, the second to the view size change. AwContents is the only place they
come together. Maybe it makes sense to combine them on one call, like in this
PS?

             nativeOnSizeChanged(mNativeAwContents, w, h, ow, oh);
         }