https://bugs.webkit.org/show_bug.cgi?id=76659

Source/WebCore:

Three major changes:

1. Modify timeToSampleFrame to round the time to the sample frame
and add support for Visual Studio to round the time in the same
way as on gcc. (The issue is that Visual Studio uses x87
instructions with 80-bit floats.)  This makes Visual Studio more
consistent with the results with gcc.

2. Change the current time variable from keeping time in seconds
to keeping time in sample frames.  This minimizes rounding except
when needed for the Javascript API.

3. Update AudioBufferSourceNode::process to use samples (instead
of time) as much as possible to reduce round-off effects.

Patch by Raymond Toy <rtoy@google.com> on 2012-01-27
Reviewed by Kenneth Russell.

Tests: Added note-grain-on test to exercise precise
timing. Existing tests (gain and audiobuffersource-playbackrate)
also cover some of these changes, and the equalpower panner test is
modified to enable the tests for the offset of the impulses.

* platform/audio/AudioUtilities.cpp:
(WebCore::AudioUtilities::timeToSampleFrame): Moved from
AudioParamTimeLine and slightly modified, and updated to round
operations consistently.  Add special flags for Visual Studio to
generate code with rounding that is consistent with gcc.
* platform/audio/AudioUtilities.h: Declare new function.
* webaudio/AudioBufferSourceNode.cpp:
(WebCore::AudioBufferSourceNode::process): Use new functions to
convert time to sample frame.  Update code to use integer
arithmetic as much as possible.
(WebCore::AudioBufferSourceNode::renderFromBuffer): Use
timeToSampleFrame to convert time to sample frame.
* webaudio/AudioContext.h: Define new currentSample method to get
the current sample.
* webaudio/AudioDestinationNode.cpp:
(WebCore::AudioDestinationNode::provideInput): Use new function to
convert sample frame to time.  Update
* webaudio/AudioDestiationNode.h: Rename m_currentTime to
m_currentSample, add method to return current Sample.  Update
currentTime() method to compute time from the current sample.
* webaudio/AudioParamTimeline.cpp:
(WebCore::AudioParamTimeline::valuesForTimeRangeImpl): Remove
timeToSampleFrame and use new function in AudioUtilities to
convert time to sample frame.

LayoutTests:

Patch by Raymond Toy <rtoy@google.com> on 2012-01-27
Reviewed by Kenneth Russell.

* webaudio/audiobuffersource-playbackrate-expected.wav: Updated.
* webaudio/gain-expected.wav: Updated.
* webaudio/resources/audio-testing.js:
(timeToSampleFrame): Utility to convert time to sample frame, to
be consistent with the actual webaudio implementation.
* webaudio/resources/panner-model-testing.js:
(checkResult): Enable the tests for the offset of the impulses.
Also fix a bug in printing the time where the max error was
found.
* webaudio/note-grain-on-timing.html: New test for noteGrainOn.
Also tests the new currentSample implemenation and
roundToSampleFrame.
* webaudio/note-grain-on-timing-expected.txt: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106162 268f45cc-cd09-0410-ab3c-d52691b4dbfc