Merge 117191 - Assertion failure running Mozilla's WebGL performance regression tests

Merge 117191 - Assertion failure running Mozilla's WebGL performance regression tests
https://bugs.webkit.org/show_bug.cgi?id=85942

Reviewed by Stephen White.

Fixed incorrect assumptions about source formats and buffer sizes
when uploading to floating-point textures. Added code paths
supporting the necessary conversions.

Tests have been added to the WebGL conformance suite which cover
these new code paths; they verify uploads of HTMLCanvasElement,
HTMLImageElement, HTMLVideoElement, and ImageData to
floating-point textures. However, because floating-point texture
support is optional, and generally only supported on bots which
run with real GPUs and not in virtual machines, it isn't feasible
to incorporate these tests as layout tests.

Ran the new WebGL conformance tests in Chromium on Linux; all
pass.

* platform/graphics/GraphicsContext3D.cpp:
(WebCore::GraphicsContext3D::extractImageData):
Properly compute size of destination buffer.

(WebCore):
Add pack/unpack routines for converting RGBA8/BGRA8 to floating point.

(WebCore::doFloatingPointPacking):
Support RGBA8 and BGRA8 source formats.

(WebCore::isFloatingPointSource):
Factored out logic for assertions.

(WebCore::GraphicsContext3D::packPixels):
Generalized assertions and logic.

* platform/graphics/cairo/GraphicsContext3DCairo.cpp:
(WebCore::GraphicsContext3D::getImageData):
Properly compute size of destination buffer.

* platform/graphics/cg/GraphicsContext3DCG.cpp:
(WebCore::GraphicsContext3D::getImageData):
Properly compute size of destination buffer.

* platform/graphics/qt/GraphicsContext3DQt.cpp:
(WebCore::GraphicsContext3D::getImageData):
Properly compute size of destination buffer.

* platform/graphics/skia/GraphicsContext3DSkia.cpp:
(WebCore::GraphicsContext3D::getImageData):
Properly compute size of destination buffer.


TBR=kbr@google.com
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=118410