chrome/android: Consume down events for mouse drag gesture.

ui/android/java/src/org/chromium/ui/base/EventForwarder.java

Index: ui/android/java/src/org/chromium/ui/base/EventForwarder.java
diff --git a/ui/android/java/src/org/chromium/ui/base/EventForwarder.java b/ui/android/java/src/org/chromium/ui/base/EventForwarder.java
index 152e5b92be21ccc320a1042722aaa5a488a15615..2d79dbd9e534cbdcf01b6f455340ed0f7e7640dd 100644
--- a/ui/android/java/src/org/chromium/ui/base/EventForwarder.java
+++ b/ui/android/java/src/org/chromium/ui/base/EventForwarder.java
@@ -190,7 +190,10 @@ public class EventForwarder {
             // and ACTION_BUTTON_RELEASE respectively because they provide
             // info about the changed-button.
             if (eventAction == MotionEvent.ACTION_DOWN || eventAction == MotionEvent.ACTION_UP) {
-                return false;
+                // While we use the action buttons for the changed state it is important to still
+                // consume the down/up events to get the complete stream for a drag gesture, which
+                // is provided using ACTION_MOVE touch events.
+                return true;
             }
 
             nativeOnMouseEvent(mNativeEventForwarder, event.getEventTime(), eventAction,