WebGL: optimize webgl.texSubImage2D(video) path. (Blink side)

Source/platform/graphics/ImageBuffer.cpp

Index: Source/platform/graphics/ImageBuffer.cpp
diff --git a/Source/platform/graphics/ImageBuffer.cpp b/Source/platform/graphics/ImageBuffer.cpp
index d1f305d1b878f65dc20522116998343b0293a356..5168e68716a6ad4e82f49eb585afbd13853e810f 100644
--- a/Source/platform/graphics/ImageBuffer.cpp
+++ b/Source/platform/graphics/ImageBuffer.cpp
@@ -178,12 +178,28 @@ WebLayer* ImageBuffer::platformLayer() const
     return m_surface->layer();
 }
 
-bool ImageBuffer::copyToPlatformTexture(WebGraphicsContext3D* context, Platform3DObject texture, GLenum internalFormat, GLenum destType, GLint level, bool premultiplyAlpha, bool flipY)
+bool ImageBuffer::copyToPlatformTexture(WebGraphicsContext3D* context, GLenum target, Platform3DObject texture,
+    GLenum internalFormat, GLenum destType, GLint level, bool premultiplyAlpha, bool flipY)
+{
+    return copyToPlatformTextureInternal(true, context, target, texture, internalFormat,
+        destType, level, 0, 0, 0, 0, premultiplyAlpha, flipY);
+}
+
+bool ImageBuffer::copySubToPlatformTexture(WebGraphicsContext3D* context, GLenum target, Platform3DObject texture,
+    GLint level, GLint xoffset, GLint yoffset, GLsizei width, GLsizei height, bool premultiplyAlpha, bool flipY)
+{
+    return copyToPlatformTextureInternal(false, context, target, texture, GL_FALSE, GL_FALSE, level,
+        xoffset, yoffset, width, height, premultiplyAlpha, flipY);
+}
+
+bool ImageBuffer::copyToPlatformTextureInternal(bool isFullCopy, WebGraphicsContext3D* context, GLenum target,
+    Platform3DObject texture, GLenum internalFormat, GLenum destType, GLint level, GLint xoffset, GLint yoffset,
+    GLsizei width, GLsizei height, bool premultiplyAlpha, bool flipY)
 {
     if (!m_surface->isAccelerated() || !isSurfaceValid())
         return false;
 
-    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(GL_TEXTURE_2D, internalFormat, destType, level))
+    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(target, internalFormat, destType, level))
         return false;
 
     RefPtr<const SkImage> textureImage = m_surface->newImageSnapshot();
@@ -215,9 +231,16 @@ bool ImageBuffer::copyToPlatformTexture(WebGraphicsContext3D* context, Platform3
     context->waitSyncPoint(mailbox->syncPoint);
     Platform3DObject sourceTexture = context->createAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, mailbox->name);
 
+    WGC3Dboolean glFlipY = flipY ? GL_FALSE : GL_TRUE;
+    WGC3Dboolean glPremultiplyAlpha = premultiplyAlpha ? GL_FALSE : GL_TRUE;
+
     // The canvas is stored in a premultiplied format, so unpremultiply if necessary.
     // The canvas is stored in an inverted position, so the flip semantics are reversed.
-    context->copyTextureCHROMIUM(GL_TEXTURE_2D, sourceTexture, texture, internalFormat, destType, flipY ? GL_FALSE : GL_TRUE, GL_FALSE, premultiplyAlpha ? GL_FALSE : GL_TRUE);
+    if (isFullCopy) {
+        context->copyTextureCHROMIUM(target, sourceTexture, texture, internalFormat, destType, glFlipY, GL_FALSE, glPremultiplyAlpha);
+    } else {
+        context->copySubTextureCHROMIUM(target, sourceTexture, texture, xoffset, yoffset, 0, 0, width, height, glFlipY, GL_FALSE, glPremultiplyAlpha);
+    }
 
     context->deleteTexture(sourceTexture);