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

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 e39393d77b2bf560d17f65b407633f8537ee986e..4b2711004d59442329cce8ce44283865f51316f0 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
@@ -1364,11 +1364,6 @@ import java.util.Map;
                 x, y, computeHorizontalScrollOffset(), computeVerticalScrollOffset());
     }
 
-    @Override
-    public boolean hasFixedPageScale() {
-        return mRenderCoordinates.hasFixedPageScale();
-    }
-
     private void hidePopupDialog() {
         SelectPopupDialog.hide(this);
         hideHandles();
@@ -2203,6 +2198,8 @@ import java.util.Map;
         if (needUpdateZoomControls) mZoomControlsDelegate.updateZoomControls();
         if (contentOffsetChanged) updateHandleScreenPositions();
 
+        updateDoubleTapZoomEnabled();
+
         // Update offsets for fullscreen.
         final float deviceScale = mRenderCoordinates.getDeviceScaleFactor();
         final float controlsOffsetPix = controlsOffsetYCss * deviceScale;
@@ -2216,6 +2213,26 @@ import java.util.Map;
         }
     }
 
+    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,