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

Source/platform/graphics/gpu/DrawingBufferTest.cpp

Index: Source/platform/graphics/gpu/DrawingBufferTest.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBufferTest.cpp b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
index e99e7630bc8521d0a07f91d0575229b3e37feff6..4ce0814f640fd052e09109e161467871c2490eb7 100644
--- a/Source/platform/graphics/gpu/DrawingBufferTest.cpp
+++ b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
@@ -357,4 +357,25 @@ TEST_F(DrawingBufferTest, verifyInsertAndWaitSyncPointCorrectly)
     EXPECT_EQ(waitSyncPoint, webContext()->mostRecentlyWaitedSyncPoint());
 }
 
+TEST_F(DrawingBufferTest, verifySetIsHiddenProperlyAffectsMailboxes)
+{
+    blink::WebExternalTextureMailbox mailbox;
+
+    // Produce mailboxes.
+    m_drawingBuffer->markContentsChanged();
+    EXPECT_TRUE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
+
+    unsigned waitSyncPoint = webContext()->insertSyncPoint();
+    mailbox.syncPoint = waitSyncPoint;
+    m_drawingBuffer->setIsHidden(true);
+    m_drawingBuffer->mailboxReleased(mailbox);
+    // m_drawingBuffer deletes mailbox immediately when hidden.
+    EXPECT_EQ(waitSyncPoint, webContext()->mostRecentlyWaitedSyncPoint());
+
+    // Fails to get mailbox when hidden.
+    EXPECT_FALSE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
+
+    m_drawingBuffer->beginDestruction();
+}
+
 } // namespace