Ensure GL initialization only happens once, and provide common init path

ui/gl/gl_switches.cc

Index: ui/gl/gl_switches.cc
diff --git a/ui/gl/gl_switches.cc b/ui/gl/gl_switches.cc
index b747d8f7ea9e5466a288eb224e68d5f367439de0..c926d4ba58aca87622928bc3d0e616e70f320071 100644
--- a/ui/gl/gl_switches.cc
+++ b/ui/gl/gl_switches.cc
@@ -71,6 +71,9 @@ const char kTestGLLib[]                     = "test-gl-lib";
 // the GL output will not be correct but tests will run faster.
 const char kDisableGLDrawingForTests[] = "disable-gl-drawing-for-tests";
 
+// Use hardware gpu, if available, for tests.
+const char kUseGpuInTests[] = "use-gpu-in-tests";
+
 // This is the list of switches passed from this file that are passed from the
 // GpuProcessHost to the GPU Process. Add your switch to this list if you need
 // to read it in the GPU process, else don't add it.