gpu: introduce glCopySubTextureCHROMIUM

gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt

Index: gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt
diff --git a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt
index ad9ca689ca90303ffa3c9342e3d70894ef7a5719..27ead406233bbe55cb63b19293386fadf8883ff3 100644
--- a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt
+++ b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt
@@ -36,9 +36,11 @@ Overview
 
 New Procedures and Functions
 
-    void glCopyTextureCHROMIUM (GLenum target, GLenum source_id,
-                                GLenum dest_id, GLint level,
-                                GLint internal_format, GLenum dest_type)
+    The command
+
+        void glCopyTextureCHROMIUM (GLenum target, GLenum source_id,
+                                    GLenum dest_id, GLint level,
+                                    GLint internal_format, GLenum dest_type)
 
     Copies the contents of texture referred to by <source_id> to texture
     <dest_id>.
@@ -90,6 +92,39 @@ New Procedures and Functions
     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.
 
+    The command
+
+        void glCopySubTextureCHROMIUM (GLenum target, GLenum source_id,
+                                       GLenum dest_id, GLint level,
+                                       GLint xoffset, GLint yoffset)
+
+    Copies the sub contents of texture referred to by <source_id> to texture
+    <dest_id>.
+
+    See CopyTextureCHROMIUM for the interpretation of the <target> and <level>
+    arguments.
+
+    <xoffset> and <yoffset> specify a texel offset in the x and y direction
+    respectively within the destination texture.
+
+    INVALID_OPERATION is generated if source internal_format and destination
+    internal_format are not one of the valid formats described above.
+
+    INVALID_VALUE is generated if <target> is not GL_TEXTURE_2D.
+
+    INVALID_OPERATION is generated if the destination texture has not been
+    defined.
+
+    INVALID_VALUE is generated if <level> is less than 0.
+
+    INVALID_VALUE may be generated if <level> >log2(max), where max is
+    the returned value of GL_MAX_TEXTURE_SIZE.
+
+    INVALID_VALUE is generated if <xoffset> < 0 , or <yoffset> < 0.
+
+    INVALID_VALUE is generated if (<xoffset> + source_width) > dest_width,
+    or (<yoffset> + source_height) > dest_height.
+
 Errors
 
     None.