Add support for the EGL_CHROMIUM_sync_control extension

Add support for the EGL_CHROMIUM_sync_control extension

This is essentially just a version of glXGetSyncValuesOML from GLX_OML_sync_control, and is used on Chrome OS to determine when the last vsync occurred. The implementation estimates the last vsync time based on the current scanline position.
BUG=

[Geoff Lang, 2013-09-17 14:04:31]

If there is an extension spec, please add it to the extensions directory.

Please also update src/libEGL/libEGL.def with the new function.

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
File src/libGLESv2/renderer/SwapChain9.cpp (right):

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
src/libGLESv2/renderer/SwapChain9.cpp:489: clamped_scanline * vsync_interval /
display_mode.Height;
Our char-per-line limit is 120, this could be a single line.

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
src/libGLESv2/renderer/SwapChain9.cpp:502: mScreenSwapCount += ((vsync_time +
vsync_interval / 2) - mLastSwapTime) / vsync_interval;
Please add a comment explaining this calculation, I'm a bit confused by the
addition of half of the vsync_interval.

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
src/libGLESv2/renderer/SwapChain9.cpp:503: *msc = mScreenSwapCount;
These lines need to be indented two more spaces.

[Jamie Madill, 2013-09-17 14:16:09]

https://codereview.appspot.com/13738043/diff/1/src/libEGL/Display.cpp
File src/libEGL/Display.cpp (right):

https://codereview.appspot.com/13738043/diff/1/src/libEGL/Display.cpp#newcode507
src/libEGL/Display.cpp:507: mExtensionString += "EGL_CHROMIUM_sync_control";
whitespace error on indent here

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
File src/libGLESv2/renderer/SwapChain11.cpp (right):

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
src/libGLESv2/renderer/SwapChain11.cpp:769: {
Any reason we couldn't include D3D11 support? Is this not necessary for D3D11? A
comment explaining the reasoning at least would be helpful.

Also minor whitespace indent error.

https://codereview.appspot.com/13738043/diff/1/src/libGLESv2/renderer/SwapCha...
src/libGLESv2/renderer/SwapChain11.cpp:771: }
nitpick: add newline

[Shannon Woods, 2013-09-17 19:05:17]

https://codereview.appspot.com/13738043/diff/1/include/EGL/eglext.h
File include/EGL/eglext.h (right):

https://codereview.appspot.com/13738043/diff/1/include/EGL/eglext.h#newcode364
include/EGL/eglext.h:364: 
If we're going to diverge eglext.h from the canonical version, I'd rather not do
so with an out-of-date version of the file.

Alternatively, the extension could be published and included in the canonical
eglext.h.

https://codereview.appspot.com/13738043/diff/1/src/libEGL/libEGL.cpp
File src/libEGL/libEGL.cpp (right):

https://codereview.appspot.com/13738043/diff/1/src/libEGL/libEGL.cpp#newcode1155
src/libEGL/libEGL.cpp:1155: EGLuint64CHROMIUM *msc, EGLuint64CHROMIUM *sbc)
Please indent this to the level where arguments begin on the previous line.