Disable double tap zoom on mobile sites, to remove 300ms click delay

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

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.content.browser;
 
 import android.app.Activity;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.pm.ActivityInfo;
@@ skipping 1346 matching lines @@
     public ContentSettings getContentSettings() {
         return mContentSettings;
     }
 
     @Override
     public boolean didUIStealScroll(float x, float y) {
         return getContentViewClient().shouldOverrideScroll(
                 x, y, computeHorizontalScrollOffset(), computeVerticalScrollOffset());
     }
 
-    @Override
-    public boolean hasFixedPageScale() {
-        return mRenderCoordinates.hasFixedPageScale();
-    }
-
     private void hidePopupDialog() {
         SelectPopupDialog.hide(this);
         hideHandles();
         hideSelectActionBar();
     }
 
     void hideSelectActionBar() {
         if (mActionMode != null) {
             mActionMode.finish();
             mActionMode = null;
@@ skipping 814 matching lines @@
                 scrollOffsetX, scrollOffsetY,
                 contentWidth, contentHeight,
                 viewportWidth, viewportHeight,
                 pageScaleFactor, minPageScaleFactor, maxPageScaleFactor,
                 contentOffsetYPix);
 
         if (needTemporarilyHideHandles) temporarilyHideTextHandles();
         if (needUpdateZoomControls) mZoomControlsDelegate.updateZoomControls();
         if (contentOffsetChanged) updateHandleScreenPositions();
 
+        updateDoubleTapZoomEnabled();
+
         // Update offsets for fullscreen.
         final float deviceScale = mRenderCoordinates.getDeviceScaleFactor();
         final float controlsOffsetPix = controlsOffsetYCss * deviceScale;
         final float overdrawBottomHeightPix = overdrawBottomHeightCss * deviceScale;
         getContentViewClient().onOffsetsForFullscreenChanged(
                 controlsOffsetPix, contentOffsetYPix, overdrawBottomHeightPix);
 
         mPendingRendererFrame = true;
         if (mBrowserAccessibilityManager != null) {
             mBrowserAccessibilityManager.notifyFrameInfoInitialized();
         }
     }
 
+    private void updateDoubleTapZoomEnabled() {
+        float pageScale = mRenderCoordinates.getPageScaleFactor();
+        float contentWidthCss = mRenderCoordinates.getContentWidthCss();
+        float windowWidthDp = pageScale * mRenderCoordinates.getLastFrameViewportWidthCss();
+
+        float minScale = mRenderCoordinates.getMinPageScaleFactor();
+        float maxScale = mRenderCoordinates.getMaxPageScaleFactor();
+
+        // We disable double-tap zoom for pages that have a width=device-width
+        // or narrower viewport (indicating that this is a mobile-optimized or
+        // responsive website), as long as the user has not pinch-zoomed in by
+        // more than 10% (in which case they might reasonably expect to be able
+        // to zoom back out using double-tap zoom).
+        // It is also disabled for pages that disallow the user from zooming in
+        // or out (even if they don't have a device-width or narrower viewport).
+        boolean enable = (contentWidthCss > windowWidthDp || pageScale >= 1.1f * minScale)
+                         && minScale != maxScale;
+        mContentViewGestureHandler.setDoubleTapZoomEnabled(enable);
+    }
+
     @SuppressWarnings("unused")
     @CalledByNative
     private void updateImeAdapter(int nativeImeAdapterAndroid, int textInputType,
             String text, int selectionStart, int selectionEnd,
             int compositionStart, int compositionEnd, boolean showImeIfNeeded) {
         TraceEvent.begin();
         mSelectionEditable = (textInputType != ImeAdapter.getTextInputTypeNone());
 
         if (mActionMode != null) mActionMode.invalidate();
 
@@ skipping 883 matching lines @@
 
     private native void nativeAttachExternalVideoSurface(
             int nativeContentViewCoreImpl, int playerId, Surface surface);
 
     private native void nativeDetachExternalVideoSurface(
             int nativeContentViewCoreImpl, int playerId);
 
     private native void nativeSetAccessibilityEnabled(
             int nativeContentViewCoreImpl, boolean enabled);
 }