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..d9c6fc734c7c977139edc4ca5927661d65590571 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 +186,28 @@ void DrawingBuffer::markLayerComposited()
     m_layerComposited = true;
 }
 
+
+void DrawingBuffer::setIsHidden(bool hidden)
+{
+    ASSERT(!m_destructionInProgress);
+    bool newHiddenValue = hidden || m_destructionInProgress;
+    if (m_isHidden == newHiddenValue)
+        return;
+
+    m_isHidden = newHiddenValue;
+    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();
@@ -192,7 +215,7 @@ blink::WebGraphicsContext3D* DrawingBuffer::context()
 
 bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox, blink::WebExternalBitmap* bitmap)
 {
-    if (!m_contentsChanged)
+    if (!m_contentsChanged || m_isHidden)
         return false;
 
     if (m_destructionInProgress) {
@@ -278,8 +301,8 @@ 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 +319,7 @@ 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();