Bug 1235234 - Fix unintentional switch fallthrough in ipc/chromium/ found by -Wimplicit-fallthrough warning. r=gcp

ipc/chromium/src/base/process_util_mac.mm:132:5 [-Wimplicit-fallthrough] unannotated fall-through between switch labels

ipc/chromium/src/base/process_util_mac.mm

@@ -129,6 +129,7 @@ bool LaunchApp(const std::vector<std::string>& argv,
       break;
     case PROCESS_ARCH_PPC:
       cpu_types[0] = CPU_TYPE_POWERPC;
+      break;
     default:
       cpu_types[0] = CPU_TYPE_ANY;
       break;