When SkFlags encounters an invalid flag, quit.

This way the user knows to change their command line.

Review URL: https://codereview.chromium.org/12881014

git-svn-id: http://skia.googlecode.com/svn/trunk@8275 2bbb7eff-a529-9590-31e7-b0007b416f81

tools/SkFlags.cpp

@@ -157,7 +157,8 @@ void SkFlags::ParseCommandLine(int argc, char** argv) {
                 flag = flag->next();
             }
             if (!flagMatched) {
-                SkDebugf("skipping unknown flag %s\n", argv[i]);
+                SkDebugf("Got unknown flag \"%s\". Exiting.\n", argv[i]);
+                exit(-1);
             }
         }
     }