Prepare SyntheticPointerAction to handle mouse actions

content/common/input/synthetic_pointer_action_params.cc

Index: content/common/input/synthetic_pointer_action_params.cc
diff --git a/content/common/input/synthetic_pointer_action_params.cc b/content/common/input/synthetic_pointer_action_params.cc
index 593413b9822e8a52668cce5488c953ec302c8854..905afe969eeb105c41ed3c019b22d9139fe41783 100644
--- a/content/common/input/synthetic_pointer_action_params.cc
+++ b/content/common/input/synthetic_pointer_action_params.cc
@@ -7,11 +7,11 @@
 namespace content {
 
 SyntheticPointerActionParams::SyntheticPointerActionParams()
-    : pointer_action_type_(PointerActionType::NOT_INITIALIZED), index_(-1) {}
+    : pointer_action_type_(PointerActionType::NOT_INITIALIZED), index_(0) {}
 
 SyntheticPointerActionParams::SyntheticPointerActionParams(
     PointerActionType type)
-    : pointer_action_type_(type), index_(-1) {}

[tdresser, 2016/07/26 12:27:41]

Do we ever end up with -1 in the index_map_ now? If not, none of the validation
code will work, will it?

[lanwei, 2016/07/28 04:47:23]

In the constructor, the sourcetype is unknown. How about I always return 0?

[tdresser, 2016/07/28 12:29:55]

I'm not clear on what your proposal is here. If you always return 0, validation
logic doesn't work, correct? (Don't we have a test that should fail in this
case?)

We could change the variable to be called "touch_index_", or something, and then
have a method called "index()" which, if the source is touch, returns the
touch_index_, and otherwise returns 0.

+    : pointer_action_type_(type), index_(0) {}
 
 SyntheticPointerActionParams::SyntheticPointerActionParams(
     const SyntheticPointerActionParams& other)