WebGL: Free temporary GPU resources held by inactive or hidden WebGL.

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 bcf1a10ae65da690d43f1828cf206946252c421a..3e70a4319fdb995d717a73289dea85a188cd3286 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -148,6 +148,7 @@ DrawingBuffer::DrawingBuffer(PassOwnPtr<blink::WebGraphicsContext3D> context,
     , m_sampleCount(0)
     , m_packAlignment(4)
     , m_destructionInProgress(false)
+    , m_isHidden(false)
     , m_contextEvictionManager(contextEvictionManager)
 {
     // Used by browser tests to detect the use of a DrawingBuffer.
@@ -185,6 +186,26 @@ void DrawingBuffer::markLayerComposited()
     m_layerComposited = true;
 }
 
+
+void DrawingBuffer::setIsHidden(bool hidden)
+{
+    ASSERT(!m_destructionInProgress);

[Ken Russell (switch to Gerrit), 2014/07/09 20:57:57]

This assert seems a little aggressive, but I do agree after re-reading
WebGLRenderingContextBase that it should never happen.

+    if (m_isHidden == hidden)
+        return;
+    m_isHidden = hidden;

[dshwang, 2014/07/09 17:40:54]

I changes m_isHidden meaning. It doesn't include m_destructionInProgress
anymore. m_isHidden is used in two places. If m_destructionInProgress should be
checked, I check it explicitly.

+    if (m_isHidden)
+        freeRecycledMailboxes();
+}
+
+void DrawingBuffer::freeRecycledMailboxes()
+{
+    if (m_recycledMailboxQueue.isEmpty())
+        return;
+    m_context->makeContextCurrent();
+    while (!m_recycledMailboxQueue.isEmpty())
+        deleteMailbox(m_recycledMailboxQueue.takeLast());
+}
+
 blink::WebGraphicsContext3D* DrawingBuffer::context()
 {
     return m_context.get();
@@ -192,6 +213,7 @@ blink::WebGraphicsContext3D* DrawingBuffer::context()
 
 bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox, blink::WebExternalBitmap* bitmap)
 {
+    ASSERT(!m_isHidden);

[dshwang, 2014/07/09 17:40:54]

As danakj@ mentioned, 'm_isHidden == true' never happens here.

     if (!m_contentsChanged)
         return false;
 
@@ -278,8 +300,8 @@ bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox,
 
 void DrawingBuffer::mailboxReleased(const blink::WebExternalTextureMailbox& mailbox)
 {
-    if (m_destructionInProgress) {
-        mailboxReleasedWhileDestructionInProgress(mailbox);
+    if (m_destructionInProgress || m_isHidden) {
+        mailboxReleasedWithoutRecycling(mailbox);
         return;
     }
 
@@ -296,7 +318,7 @@ void DrawingBuffer::mailboxReleased(const blink::WebExternalTextureMailbox& mail
     ASSERT_NOT_REACHED();
 }
 
-void DrawingBuffer::mailboxReleasedWhileDestructionInProgress(const blink::WebExternalTextureMailbox& mailbox)
+void DrawingBuffer::mailboxReleasedWithoutRecycling(const blink::WebExternalTextureMailbox& mailbox)
 {
     ASSERT(m_textureMailboxes.size());
     m_context->makeContextCurrent();