rename tracing parameter to be more consistent with other methods

BUG=skia:
R=bsalomon@google.com

Author: humper@google.com

Review URL: https://codereview.chromium.org/136753013

git-svn-id: http://skia.googlecode.com/svn/trunk@13287 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkEventTracer.cpp b/src/utils/SkEventTracer.cpp
index 707e94b..529fca3 100644
--- a/src/utils/SkEventTracer.cpp
+++ b/src/utils/SkEventTracer.cpp
@@ -30,7 +30,7 @@
         return &no;
     };
     virtual const char* getCategoryGroupName(
-      const uint8_t* category_group_enabled) SK_OVERRIDE {
+      const uint8_t* categoryEnabledFlag) SK_OVERRIDE {
         static const char* dummy = "dummy";
         return dummy;
     };