Prepare SyntheticPointerAction to handle touch actions for multiple fingers

content/browser/renderer_host/input/synthetic_gesture_target_base.cc

Index: content/browser/renderer_host/input/synthetic_gesture_target_base.cc
diff --git a/content/browser/renderer_host/input/synthetic_gesture_target_base.cc b/content/browser/renderer_host/input/synthetic_gesture_target_base.cc
index e1fd3b06f3136572db2eb024dcee478faa9f961e..5b54e1adbd9e4175e4ff461170c7005e4b5ca71d 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_target_base.cc
+++ b/content/browser/renderer_host/input/synthetic_gesture_target_base.cc
@@ -55,13 +55,11 @@ void SyntheticGestureTargetBase::DispatchInputEventToPlatform(
         static_cast<const WebTouchEvent&>(event);
 
     // Check that all touch pointers are within the content bounds.
-    if (web_touch.type == WebInputEvent::TouchStart) {
-      for (unsigned i = 0; i < web_touch.touchesLength; i++)
-        CHECK(web_touch.touches[i].state != WebTouchPoint::StatePressed ||
-              PointIsWithinContents(web_touch.touches[i].position.x,
-                                    web_touch.touches[i].position.y))
-            << "Touch coordinates are not within content bounds on TouchStart.";
-    }
+    for (unsigned i = 0; i < web_touch.touchesLength; i++)
+      CHECK(web_touch.touches[i].state != WebTouchPoint::StatePressed ||
+            PointIsWithinContents(web_touch.touches[i].position.x,
+                                  web_touch.touches[i].position.y))
+          << "Touch coordinates are not within content bounds on TouchStart.";

[tdresser, 2016/05/13 13:58:04]

Is dragging your finger outside the window reasonable?

Also, the log text still references TouchStart.

[lanwei, 2016/05/19 16:04:13]

Because when we combine actions together, sometimes touch event's type is not
TouchStart, but it may have a touch point which is a press, so I need to check
for all the touch points' state. 

 
     DispatchWebTouchEventToPlatform(web_touch, latency_info);
   } else if (event.type == WebInputEvent::MouseWheel) {