Define a --force-gpu-rasterization flag

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index 95018a72cb91200797c3ba7627f459a84f906cbe..140a5a1da72dae132b0d071bf865e30209b6daeb 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -5535,7 +5535,8 @@ TEST_F(LayerTreeHostImplTest, MemoryPolicy) {
       gpu::MemoryAllocation::CUTOFF_ALLOW_NOTHING);
 
   // GPU rasterization should be disabled by default.
-  EXPECT_EQ(host_impl_->settings().gpu_rasterization, false);
+  EXPECT_EQ(LayerTreeSettings::GpuRasterizationDisabled,
+            host_impl_->settings().gpu_rasterization_state);
 
   host_impl_->SetVisible(true);
   host_impl_->SetMemoryPolicy(policy1);
@@ -5553,7 +5554,7 @@ TEST_F(LayerTreeHostImplTest, MemoryPolicy) {
   // Now enable GPU rasterization and test if we get required only cutoff,
   // when visible.
   LayerTreeSettings settings;
-  settings.gpu_rasterization = true;
+  settings.gpu_rasterization_state = LayerTreeSettings::GpuRasterizationForced;
   host_impl_ = LayerTreeHostImpl::Create(
       settings, this, &proxy_, &stats_instrumentation_, NULL, 0);