Cleanup: Use SkAutoGraphics in gm and tests.

BUG=None
R=bsalomon@google.com

Review URL: https://codereview.chromium.org/704413002
diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index da0f38f..cd3f03a 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -2257,7 +2257,7 @@
     }
 #endif
 
-    SkGraphics::Init();
+    SkAutoGraphics ag;
 
     setSystemPreferences();
     GMMain gmmain;
@@ -2474,7 +2474,6 @@
 
     delete grFactory;
 #endif
-    SkGraphics::Term();
 
     return (reportError) ? -1 : 0;
 }