Update the SkDocument interface to allow for 1) abort won't emit pdf, 2) close can report success/f…

gm/gm_error.h

Index: gm/gm_error.h
diff --git a/gm/gm_error.h b/gm/gm_error.h
index e442f5d894376436773a8bc8372b9a096b485671..e2274c4ffaccbd3cccc2e510a7f90007d2ade663 100644
--- a/gm/gm_error.h
+++ b/gm/gm_error.h
@@ -28,6 +28,7 @@ namespace skiagm {
 
         kIntentionallySkipped_ErrorType,
         kRenderModeMismatch_ErrorType,
+        kGeneratePdfFailed_ErrorType,
         kExpectationsMismatch_ErrorType,
         kMissingExpectations_ErrorType,
         kWritingReferenceImage_ErrorType,
@@ -45,6 +46,8 @@ namespace skiagm {
             return "IntentionallySkipped";
         case kRenderModeMismatch_ErrorType:
             return "RenderModeMismatch";
+        case kGeneratePdfFailed_ErrorType:
+            return "GeneratePdfFailed";
         case kExpectationsMismatch_ErrorType:
             return "ExpectationsMismatch";
         case kMissingExpectations_ErrorType: