Plumbing explicit share groups through context creation

content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h

Index: content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h
diff --git a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h
index a50c9d50d8317ff5914f8534c66a73e9f5002b4d..faaf944bfda5726684aead0c7b2854876d09ac8e 100644
--- a/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h
+++ b/content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.h
@@ -11,6 +11,7 @@
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/synchronization/lock.h"
 #include "content/common/content_export.h"
 #include "content/common/gpu/client/command_buffer_proxy_impl.h"
 #include "third_party/WebKit/public/platform/WebGraphicsContext3D.h"
@@ -79,7 +80,8 @@ class WebGraphicsContext3DCommandBufferImpl
       GpuChannelHost* host,
       const Attributes& attributes,
       bool bind_generates_resources,
-      const SharedMemoryLimits& limits);
+      const SharedMemoryLimits& limits,
+      WebGraphicsContext3DCommandBufferImpl* share_context);
 
   virtual ~WebGraphicsContext3DCommandBufferImpl();
 
@@ -108,7 +110,8 @@ class WebGraphicsContext3DCommandBufferImpl
           GpuChannelHost* host,
           const WebGraphicsContext3D::Attributes& attributes,
           const GURL& active_url,
-          const SharedMemoryLimits& limits);
+          const SharedMemoryLimits& limits,
+          WebGraphicsContext3D* share_context);
 
   size_t GetMappedMemoryLimit() {
     return mem_limits_.mapped_memory_reclaim_limit;
@@ -658,13 +661,58 @@ class WebGraphicsContext3DCommandBufferImpl
   };
   friend class WebGraphicsContext3DErrorMessageCallback;
 
+  class ShareGroup : public base::RefCountedThreadSafe<ShareGroup> {
+   public:
+    ShareGroup();
+
+    WebGraphicsContext3DCommandBufferImpl* GetAnyContext() {

[piman, 2013/12/12 23:56:39]

nit: maybe append "Locked" to these functions to make it explicit that the lock
is expected to be held. It's not obvious at the call site that AddContext and
RemoveContext are different in that respect.

+      // In order to ensure that the context returned is not removed while
+      // in use the share group's lock should be aquired before calling this
+      // function.
+      lock_.AssertAcquired();
+      if (contexts_.empty())
+        return NULL;
+      return contexts_.front();
+    }
+
+    void AddContext(WebGraphicsContext3DCommandBufferImpl* context) {
+      lock_.AssertAcquired();
+      contexts_.push_back(context);
+    }
+
+    void RemoveContext(WebGraphicsContext3DCommandBufferImpl* context) {
+      base::AutoLock auto_lock(lock_);
+      contexts_.erase(std::remove(contexts_.begin(), contexts_.end(), context),
+          contexts_.end());
+    }
+
+    void RemoveAllContexts() {
+      base::AutoLock auto_lock(lock_);
+      contexts_.clear();
+    }
+
+    base::Lock& lock() {
+      return lock_;
+    }
+
+   private:
+    friend class base::RefCountedThreadSafe<ShareGroup>;
+    ~ShareGroup();
+
+    std::vector<WebGraphicsContext3DCommandBufferImpl*> contexts_;
+    base::Lock lock_;
+
+    DISALLOW_COPY_AND_ASSIGN(ShareGroup);
+  };
+
   // Initialize the underlying GL context. May be called multiple times; second
   // and subsequent calls are ignored. Must be called from the thread that is
   // going to use this object to issue GL commands (which might not be the main
   // thread).
   bool MaybeInitializeGL();
 
-  bool InitializeCommandBuffer(bool onscreen);
+  bool InitializeCommandBuffer(bool onscreen,
+      WebGraphicsContext3DCommandBufferImpl* share_context);
 
   void Destroy();
 
@@ -723,6 +771,7 @@ class WebGraphicsContext3DCommandBufferImpl
   SharedMemoryLimits mem_limits_;
 
   uint32_t flush_id_;
+  scoped_refptr<ShareGroup> share_group_;
 };
 
 }  // namespace content