Revert of 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 3e70a4319fdb995d717a73289dea85a188cd3286..bcf1a10ae65da690d43f1828cf206946252c421a 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -148,7 +148,6 @@
     , 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.
@@ -186,26 +185,6 @@
     m_layerComposited = true;
 }
 
-
-void DrawingBuffer::setIsHidden(bool hidden)
-{
-    ASSERT(!m_destructionInProgress);
-    if (m_isHidden == hidden)
-        return;
-    m_isHidden = hidden;
-    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();
@@ -213,7 +192,6 @@
 
 bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox, blink::WebExternalBitmap* bitmap)
 {
-    ASSERT(!m_isHidden);
     if (!m_contentsChanged)
         return false;
 
@@ -300,8 +278,8 @@
 
 void DrawingBuffer::mailboxReleased(const blink::WebExternalTextureMailbox& mailbox)
 {
-    if (m_destructionInProgress || m_isHidden) {
-        mailboxReleasedWithoutRecycling(mailbox);
+    if (m_destructionInProgress) {
+        mailboxReleasedWhileDestructionInProgress(mailbox);
         return;
     }
 
@@ -318,7 +296,7 @@
     ASSERT_NOT_REACHED();
 }
 
-void DrawingBuffer::mailboxReleasedWithoutRecycling(const blink::WebExternalTextureMailbox& mailbox)
+void DrawingBuffer::mailboxReleasedWhileDestructionInProgress(const blink::WebExternalTextureMailbox& mailbox)
 {
     ASSERT(m_textureMailboxes.size());
     m_context->makeContextCurrent();