WebView: carefully check size for SafeBrowsing interstitial

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 9ebbb5b57ef8576cac1111b73192d98c93ad29ca..95ef94d1a9e1d92b56eab66af4cf7cd624b2090c 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -80,6 +80,7 @@ import org.chromium.ui.base.ActivityWindowAndroid;
 import org.chromium.ui.base.PageTransition;
 import org.chromium.ui.base.ViewAndroidDelegate;
 import org.chromium.ui.base.WindowAndroid;
+import org.chromium.ui.display.DisplayAndroid;
 import org.chromium.ui.display.DisplayAndroid.DisplayAndroidObserver;
 
 import java.io.File;
@@ -119,6 +120,8 @@ public class AwContents implements SmartClipProvider {
     private static final boolean FORCE_AUXILIARY_BITMAP_RENDERING =
             "goldfish".equals(Build.HARDWARE) || "ranchu".equals(Build.HARDWARE);
 
+    private static final double MIN_SCREEN_PERCENTAGE_FOR_INTERSTITIAL = 0.7;
+
     /**
      * WebKit hit test related data structure. These are used to implement
      * getHitTestResult, requestFocusNodeHref, requestImageRef methods in WebView.
@@ -2913,20 +2916,52 @@ public class AwContents implements SmartClipProvider {
         }
     }
 
-    @CalledByNative
-    private boolean canShowInterstitial() {
+    /**
+     * Determine if at least one edge of the WebView extends over the edge of the device screen.
+     */
+    private boolean extendsOffDeviceScreen() {
         int loc[] = new int[2];
         mContainerView.getLocationOnScreen(loc);
-        // TODO(sgurun) implement a better strategy here.
-        if (mContainerView.getWidth() < 500 || mContainerView.getHeight() < 500) {
-            return false;
+        int x = loc[0];
+        int y = loc[1];
+        DisplayAndroid displayAndroid = mWindowAndroid.getWindowAndroid().getDisplay();
+        if (x < 0 || y < 0 || x + mContainerView.getWidth() > displayAndroid.getDisplayWidth()
+                || y + mContainerView.getHeight() > displayAndroid.getDisplayHeight()) {
+            return true;
         }
-        if (mContainerView.getVisibility() != View.VISIBLE) {
-            return false;
-        }
-        // TODO(timvolodine) other potential improvements mentioned:
-        // consider content, not attached webviews, giant webviews, ..
-        return true;
+        return false;
+    }
+
+    /**
+     * Determine if it's reasonable to show any sort of interstitial. If the WebView is not visible,
+     * the user may not be able to interact with the UI.
+     * @return true if the WebView is visible
+     */
+    @VisibleForTesting
+    protected boolean canShowInterstitial() {
+        return mIsAttachedToWindow && mIsViewVisible;
+    }
+
+    /**
+     * Determine if it's suitable to show the interstitial for browsers and main UIs. If the WebView
+     * is close to full-screen, we assume the app is using it as the main UI, so we show the same
+     * interstital Chrome uses. Otherwise, we assume the WebView is part of a larger composed page,
+     * and will show a different interstitial.
+     * @return true if the WebView should display the large interstitial
+     */
+    @VisibleForTesting
+    @CalledByNative
+    protected boolean canShowBigInterstitial() {
+        if (!canShowInterstitial()) return false;
+        if (extendsOffDeviceScreen()) return false;
+
+        DisplayAndroid displayAndroid = mWindowAndroid.getWindowAndroid().getDisplay();
+        double percentOfScreenHeight =
+                (double) mContainerView.getHeight() / displayAndroid.getDisplayHeight();
+
+        // If the WebView is full width and most of the height, it's probably the main UI.
+        return mContainerView.getWidth() == displayAndroid.getDisplayWidth()
+                && percentOfScreenHeight >= MIN_SCREEN_PERCENTAGE_FOR_INTERSTITIAL;
     }
 
     @VisibleForTesting