Add flag to enable rendering of text using signed distance fields.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 08016d760e1858be4431575e2cf3e711ccbc583c..a73143509918e40cb2aa4104de99578eee868ef4 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -431,6 +431,13 @@ void RenderThreadImpl::Init() {
   is_gpu_rasterization_forced_ =
       command_line.HasSwitch(switches::kForceGpuRasterization);
 
+  if (command_line.HasSwitch(switches::kDisableDistanceFieldText)) {
+    is_distance_field_text_enabled_ = false;
+  } else if (command_line.HasSwitch(switches::kEnableDistanceFieldText)) {
+    is_distance_field_text_enabled_ =
+        is_gpu_rasterization_enabled_ || is_gpu_rasterization_forced_;
+  }
+
   is_low_res_tiling_enabled_ = true;
   if (command_line.HasSwitch(switches::kDisableLowResTiling) &&
       !command_line.HasSwitch(switches::kEnableLowResTiling)) {