Fix zero size buffer robust init crash.

src/libANGLE/Buffer.cpp

@@ -70,8 +70,9 @@ Error Buffer::bufferData(const Context *context,
     const void *dataForImpl = data;
 
     // If we are using robust resource init, make sure the buffer starts cleared.
+    // Note: the Context is checked for nullptr because of some testing code.
     // TODO(jmadill): Investigate lazier clearing.
-    if (context && context->getGLState().isRobustResourceInitEnabled() && data == nullptr)
+    if (context && context->getGLState().isRobustResourceInitEnabled() && !data && size > 0)
     {
         angle::MemoryBuffer *scratchBuffer = nullptr;
         ANGLE_TRY(context->getScratchBuffer(static_cast<size_t>(size), &scratchBuffer));

src/tests/gl_tests/RobustResourceInitTest.cpp

@@ -178,6 +178,19 @@ TEST_P(RobustResourceInitTest, BufferData)
     EXPECT_EQ(expected, actual);
 }
 
+// Regression test for passing a zero size init buffer with the extension.
+TEST_P(RobustResourceInitTest, BufferDataZeroSize)
+{
+    if (!setup())
+    {
+        return;
+    }
+
+    GLBuffer buffer;
+    glBindBuffer(GL_ARRAY_BUFFER, buffer);
+    glBufferData(GL_ARRAY_BUFFER, 0, nullptr, GL_STATIC_DRAW);
+}
+
 ANGLE_INSTANTIATE_TEST(RobustResourceInitTest,
                        ES2_D3D9(),
                        ES2_D3D11(),