Re-submission of http://codereview.chromium.org/9968113

This version corrects the problem that caussed the revert of the above issue.  The shaders used by the extension were specifying a precision, which is not supported on desktop GL.  The shaders now conditionally specify the precision. 

------------------------------------------------------

Introduction of CHROMIUM_copy_texture extension that respects pixel-store semantics, and allows copying of BGRA textures.

OpenGL ES does not natively allow for copying textures with a BGRA format. The EXT_texture_format_BGRA8888 extension does not specify support for glCopyTexImage calls on these textures.

This extension provides a routine to perform texture copies to/from BGRA-backed textures that also respects the following CHROMIUM pixel storage modifiers:
UNPACK_FLIP_Y_CHROMIUM
UNPACK_PREMULTIPLY_ALPHA_CHROMIUM

This extension will be useful for the following purposes:
- Copying accelerated Canvas2D contents to WebGL textures without a software readback. (And potentially the same for video-webgl texture copies.)
- Copying Canvas2D contents to the compositor backing store.

BUG=101051
TEST=none

Review URL: http://codereview.chromium.org/10124016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133213 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 66 insertions, 0 deletions

diff --git a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt
new file mode 100644
index 0000000..c48ac39
--- /dev/null
+++ b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt
@@ -0,0 +1,66 @@
+Name
+
+    CHROMIUM_copy_texture
+
+Name Strings
+
+    GL_CHROMIUM_copy_texture
+
+Version
+
+    Last Modifed Date: April 3, 2012
+
+Dependencies
+
+    OpenGL ES 2.0 is required.
+
+    CHROMIUM_flipy affects the definition of this extension.
+    EXT_texture_format_BGRA8888 affects the definition of this extension.
+
+Overview
+
+    This extension expands on the functionality provided by the
+    glCopyTexImage2D command.  A new function is exported,
+    glCopyTextureCHROMIUM, that performs the same copy operation as
+    glCopyTexImage2D, while respecting the pixel-storage modifiers
+    UNPACK_FLIP_Y_CHROMIUM and GL_UNPACK_PREMULTIPLY_ALPHA_CHROMIUM.
+
+    The extension also supports copying BGRA textures, which is not explicitly
+    granted by EXT_texture_format_BGRA8888.
+
+New Procedures and Functions
+
+    void glCopyTextureCHROMIUM (GLenum target, GLenum source_id,
+                                GLenum dest_id, GLint level)
+
+    Copies the contents of texture referred to by <source_id> to texture
+    <dest_id>.
+
+    Texture level 0 is copied from the source image to level <level> of the
+    destination texture.
+
+    <target> uses the same parameters as TexImage2D.
+
+    INVALID_VALUE is generated if <target> is not GL_TEXTURE_2D.
+
+    INVALID_VALUE is generated if <source_id> or <dest_id> are not valid texture
+    objects.
+
+    INVALID_VALUE is generated if <level> is not a valid level of the
+    destination texture, or if level 0 of the source texture is not defined.
+
+Errors
+
+    None.
+
+New Tokens
+
+    None.
+
+New State
+
+    None.
+
+Revision History
+
+    8/1/2011    Documented the extension