Share Group plumbing in Blink; Remove WebGL from default share group

Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBuffer.cpp b/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 0336f952791f712d03f133190914d3d5175f4789..fb7104a099facd1a51b7bf2fa6a62f134362ea38 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -329,14 +329,34 @@ bool DrawingBuffer::copyToPlatformTexture(blink::WebGraphicsContext3D* context,
         }
         m_context->flush();
     }
-    Platform3DObject sourceTexture = m_colorBuffer;
 
-    if (!context->makeContextCurrent())
+    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
         return false;
 
-    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
+    GLint boundTexture = 0;
+    m_context->getIntegerv(GL_TEXTURE_BINDING_2D, &boundTexture);
+
+    // Contexts may be in a different share group. We must transfer the texture through a mailbox first
+    RefPtr<MailboxInfo> bufferMailbox = adoptRef(new MailboxInfo());
+    m_context->genMailboxCHROMIUM(bufferMailbox->mailbox.name);
+    m_context->bindTexture(GL_TEXTURE_2D, m_colorBuffer);
+    m_context->produceTextureCHROMIUM(GL_TEXTURE_2D, bufferMailbox->mailbox.name);
+    m_context->flush();
+
+    bufferMailbox->mailbox.syncPoint = m_context->insertSyncPoint();
+    m_context->waitSyncPoint(bufferMailbox->mailbox.syncPoint);

[piman, 2014/03/11 00:02:24]

This is essentially a noop. You insert a sync point in one context, and wait on
the same context. What you should do instead is move the wait onto |context|
before the consumeTextureCHROMIUM.

+
+    m_context->bindTexture(GL_TEXTURE_2D, boundTexture);
+
+    if (!context->makeContextCurrent())
         return false;
 
+    Platform3DObject sourceTexture = context->createTexture();
+
+    context->getIntegerv(GL_TEXTURE_BINDING_2D, &boundTexture);
+    context->bindTexture(GL_TEXTURE_2D, sourceTexture);
+    context->consumeTextureCHROMIUM(GL_TEXTURE_2D, bufferMailbox->mailbox.name);
+
     bool unpackPremultiplyAlphaNeeded = false;
     bool unpackUnpremultiplyAlphaNeeded = false;
     if (m_attributes.alpha && m_attributes.premultipliedAlpha && !premultiplyAlpha)
@@ -351,6 +371,10 @@ bool DrawingBuffer::copyToPlatformTexture(blink::WebGraphicsContext3D* context,
     context->pixelStorei(GC3D_UNPACK_FLIP_Y_CHROMIUM, false);
     context->pixelStorei(GC3D_UNPACK_UNPREMULTIPLY_ALPHA_CHROMIUM, false);
     context->pixelStorei(GC3D_UNPACK_PREMULTIPLY_ALPHA_CHROMIUM, false);
+
+    context->bindTexture(GL_TEXTURE_2D, boundTexture);
+    context->deleteTexture(sourceTexture);
+
     context->flush();

[piman, 2014/03/11 00:02:24]

If you wanted to be thorough, you would want to insert a sync point on
|context|, and wait on |m_context| here. This would ensure |m_context| can't
delete the texture before |context| had a chance to consume it.

(since everything is in the same channel currently, you won't see it as a race
today, but we might in the future).

 
     return true;