Resize only the virtual viewport when the OSK triggers a resize.

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
index 162d1fa3d260bacf4d5b0edd52bc7e306bf99bb9..c4adf509e3ea95b487f473471618826161d6fa0f 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
@@ -205,6 +205,7 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
     private ActivityWindowAndroid mWindowAndroid;
     private ChromeFullscreenManager mFullscreenManager;
     private CompositorViewHolder mCompositorViewHolder;
+    private InsetObserverView mInsetObserverView;
     private ContextualSearchManager mContextualSearchManager;
     private ReaderModeManager mReaderModeManager;
     private SnackbarManager mSnackbarManager;
@@ -352,8 +353,18 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
         // black status bar
         ApiCompatibilityUtils.setStatusBarColor(getWindow(), Color.BLACK);
 
+        ViewGroup rootView = (ViewGroup) getWindow().getDecorView().getRootView();
         mCompositorViewHolder = (CompositorViewHolder) findViewById(R.id.compositor_view_holder);
-        mCompositorViewHolder.setRootView(getWindow().getDecorView().getRootView());
+        mCompositorViewHolder.setRootView(rootView);
+
+        // Setting fitsSystemWindows to false ensures that the root view doesn't consume the insets.
+        rootView.setFitsSystemWindows(false);
+
+        // Add a custom view right after the root view that stores the insets to access later.
+        // ContentViewCore needs the insets to determine the portion of the screen obscured by
+        // non-content displaying things such as the OSK.
+        mInsetObserverView = InsetObserverView.create(this);
+        rootView.addView(mInsetObserverView, 0);
     }
 
     /**
@@ -1059,6 +1070,15 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
         return mTabModelSelector;
     }
 
+    /**
+     * Returns the {@link InsetObserverView} that has the current system window
+     * insets information.
+     * @return The {@link InsetObserverView}, possibly null.
+     */
+    public InsetObserverView getInsetObserverView() {
+        return mInsetObserverView;
+    }
+
     @Override
     public TabCreatorManager.TabCreator getTabCreator(boolean incognito) {
         return incognito ? mIncognitoTabCreator : mRegularTabCreator;