Determine WebGL back-buffer on Mali-400 GPU

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 007c41bbc667e6ebc322b765ccb90b5195a5beb0..db38a9e5e27a53186642fac4cc624e268a771cbc 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -105,6 +105,11 @@ PassRefPtr<DrawingBuffer> DrawingBuffer::create(PassOwnPtr<WebGraphicsContext3D>
         extensionsUtil->ensureExtensionEnabled("GL_EXT_discard_framebuffer");
 
     RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(context, extensionsUtil.release(), multisampleSupported, packedDepthStencilSupported, discardFramebufferSupported, preserve, requestedAttributes));
+    Platform::current()->getGPUBlackList(&drawingBuffer->m_gpuBlackList);
+    // determineRGBTextureSupport() if GL_RGB not supported
+    if (!drawingBuffer->gpuBlackList().IsRGBTextureSupported())
+        drawingBuffer->determineRGBTextureSupport();
+
     if (!drawingBuffer->initialize(size)) {
         drawingBuffer->beginDestruction();
         return PassRefPtr<DrawingBuffer>();
@@ -150,6 +155,7 @@ DrawingBuffer::DrawingBuffer(PassOwnPtr<WebGraphicsContext3D> context,
     , m_destructionInProgress(false)
     , m_isHidden(false)
     , m_filterQuality(kLow_SkFilterQuality)
+    , m_RGBTextureSupported(true)
 {
     // Used by browser tests to detect the use of a DrawingBuffer.
     TRACE_EVENT_INSTANT0("test_gpu", "DrawingBufferCreation", TRACE_EVENT_SCOPE_GLOBAL);
@@ -403,7 +409,7 @@ bool DrawingBuffer::initialize(const IntSize& size)
         return false;
     }
 
-    if (m_requestedAttributes.alpha) {
+    if (m_requestedAttributes.alpha || !isRGBTextureSupported()) {
         m_internalColorFormat = GL_RGBA;
         m_colorFormat = GL_RGBA;
         m_internalRenderbufferFormat = GL_RGBA8_OES;
@@ -715,6 +721,9 @@ void DrawingBuffer::clearFramebuffers(GLbitfield clearMask)
 
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO ? m_multisampleFBO : m_fbo);
     m_context->clear(clearMask);
+
+    if (!m_requestedAttributes.alpha && !isRGBTextureSupported())
+        m_context->colorMask(true, true, true, false);
 }
 
 void DrawingBuffer::setSize(const IntSize& size)
@@ -987,4 +996,26 @@ void DrawingBuffer::deleteChromiumImageForTexture(TextureInfo* info)
     }
 }
 
+void DrawingBuffer::determineRGBTextureSupport()
+{
+    // One time validation is required for GL_RGB texture
+    // so that DrawingBuffer can choose format for the backbuffer correctly.
+    // DrawingBuffer tries to allocate GL_RGB texture in case of alpha attribute false
+    // and fails because GL_RGB not supported on specific GPU's (e.g Mali- 2/3/400 family).
+    Platform3DObject fbo = m_context->createFramebuffer();
+    m_context->bindFramebuffer(GL_FRAMEBUFFER, fbo);
+    unsigned offscreenRGBTexture = createColorTexture();
+    m_context->texImage2D(GL_TEXTURE_2D, 0, GL_RGB, 1, 1, 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
+    m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, offscreenRGBTexture, 0);
+    m_RGBTextureSupported = m_context->checkFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE;
+
+    if (fbo) {
+        m_context->deleteFramebuffer(fbo);
+        m_context->bindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+
+    if (offscreenRGBTexture)
+        m_context->deleteTexture(offscreenRGBTexture);
+}
+
 } // namespace blink