Add HandleInputEventAck message to allow out-of-process plugins to respond to user gestures.

Add HandleInputEventAck message to allow out-of-process plugins to respond to user gestures.
Modifies PluginInstance to track pending user gestures by timestamp.
Modifies ppapi/tests/test_fullscreen to not test that SetFullscreen and BindGraphics fail while fullscreen changes are pending. Because of how PluginInstance reports view changed events, these will likely fail due to race conditions.
BUG=73070
TEST=ui_tests, --gtest_filter=*PPAPITest.Fullscreen

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=125768

[bbudge, 2012-03-02 01:27:18]

Elevated this because of GTalk Pepper plugin. Looking for direction on overall
shape of the patch. I haven't tested this (will enable OOP Proxy tests to do
so.)

[brettw, 2012-03-02 05:48:48]

Is it possible to keep the timestamp of only the most recent input event? When
handling acks, we can throw away ones with older timestamps since the "gesture"
is being kept open with newer ones.

[bbudge, 2012-03-02 21:49:17]

Changed to only keep a single pending user gesture.

One weakness of this scheme is that if ClosePendingUserGesture isn't called
(malicious or compromised plugin) and no additional input events are routed to
the plugin (which will clear the pending user gesture after 2 seconds) then the
user gesture stays open. We could modify the code that checks for a user gesture
(currently only in SetFullscreen) to compare the user gesture timestamp with the
current time (base::Time::Now()) to see if the user gesture is still valid.

[brettw, 2012-03-02 23:29:46]

Yeah, I was envisioning some kind of check that would test the timeout before
any user-gesture-needing-calls.

[bbudge, 2012-03-03 02:18:08]

I modified the CL to measure elapsed time and left in the ACK message so well
behaved plugins go by the rules. I will work on ppapi_uitests next week and try
to get all of our failing tests working again. On Windows at least, I think the
out-of-process test may now be working. My last patch had a bug.

[bbudge, 2012-03-07 21:51:31]

Modified the tests to accept a variable number of DidChangeView notifications.
Depending on an exact sequence of notifications is likely to break as we change
the implementation. The test now waits until it receives the desired state
change. The downside of this is that if it fails, it will now time out, which is
slower.

[bbudge, 2012-03-08 01:22:28]

Looks like PPAPITest.Fullscreen and OutOfProcessPPAPITest.Fullscreen are passing
on all platforms.

[brettw, 2012-03-08 22:17:33]

lgtm

[commit-bot: I haz the power, 2012-03-08 22:28:16]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/bbudge@chromium.org/9558009/26018

[commit-bot: I haz the power, 2012-03-09 02:08:35]

Change committed as 125768