Explicitly suppress scrolling for wheel events that will trigger zooming

content/common/input/synthetic_web_input_event_builders.cc

Index: content/common/input/synthetic_web_input_event_builders.cc
diff --git a/content/common/input/synthetic_web_input_event_builders.cc b/content/common/input/synthetic_web_input_event_builders.cc
index d3addb67918cc46a16e8e14ec3124a9db9aa6f88..e5f18af585bc3098bff700036d1c01305602f9e5 100644
--- a/content/common/input/synthetic_web_input_event_builders.cc
+++ b/content/common/input/synthetic_web_input_event_builders.cc
@@ -68,6 +68,9 @@ WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(float dx,
     result.wheelTicksY = dy > 0.0f ? 1.0f : -1.0f;
   result.modifiers = modifiers;
   result.hasPreciseScrollingDeltas = precise;
+  if ((modifiers & blink::WebInputEvent::ControlKey) && !precise) {

[Rick Byers, 2014/12/12 22:20:29]

Which tests fail if you just unconditionally set canScroll to true here?  It's a
little odd that we're baking Aura's logic into the syntehtic event builders used
by tests - even on Mac where the logic doesn't apply.

Ideally your CL would need to update WebContentsImplTest::HandleWheelEvent to
explicitly set canScroll to false on the event.  Then you'd also be able to test
that a canScroll=true event doesn't ever also cause zooming.

In particular, look at the part of the test that says "Events containing precise
scrolling deltas also shouldn't result in ...".  Previously it was testing
something valuable.  Now after your CL it's really testing the behavior of the
synthetic event building code here, not the code in the product that actually
pays attention to hasPreciseDeltas!

[lanwei, 2014/12/17 23:16:40]

Done.

+    result.canScroll = false;
+  }
   return result;
 }