mac: Remove GPU bug workarounds for OS X versions before 10.9

gpu/command_buffer/tests/gl_iosurface_readback_workaround_unittest.cc

Index: gpu/command_buffer/tests/gl_iosurface_readback_workaround_unittest.cc
diff --git a/gpu/command_buffer/tests/gl_iosurface_readback_workaround_unittest.cc b/gpu/command_buffer/tests/gl_iosurface_readback_workaround_unittest.cc
index d4ddb95fc181309717eb35ea25b639806ca8e65b..ea052f0ae94b817b6ca1aecdb20fffcfa53a11e5 100644
--- a/gpu/command_buffer/tests/gl_iosurface_readback_workaround_unittest.cc
+++ b/gpu/command_buffer/tests/gl_iosurface_readback_workaround_unittest.cc
@@ -29,13 +29,9 @@ class GLIOSurfaceReadbackWorkaroundTest : public testing::Test {
 
  protected:
   void SetUp() override {
-      base::CommandLine command_line(0, NULL);
-      command_line.AppendSwitchASCII(
-          switches::kGpuDriverBugWorkarounds,
-          base::IntToString(gpu::IOSURFACE_READBACK_WORKAROUND));
-      gl_.InitializeWithCommandLine(GLManager::Options(), command_line);
-      gl_.set_use_iosurface_memory_buffers(true);
-      DCHECK(gl_.workarounds().iosurface_readback_workaround);
+    base::CommandLine command_line(0, NULL);
+    gl_.InitializeWithCommandLine(GLManager::Options(), command_line);
+    gl_.set_use_iosurface_memory_buffers(true);
   }
 
   void TearDown() override {