Fixed issue in MallocHooks where a MallocHookScope was accidentally removed during a merge, causing…

runtime/vm/os_fuchsia.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_OS_FUCHSIA)
 
 #include "vm/os.h"
 
 #include <errno.h>
@@ skipping 159 matching lines @@
 void OS::SleepMicros(int64_t micros) {
   mx_nanosleep(micros * kNanosecondsPerMicrosecond);
 }
 
 
 void OS::DebugBreak() {
   UNIMPLEMENTED();
 }
 
 
+uintptr_t DART_NOINLINE OS::GetProgramCounter() {
+  return reinterpret_cast<uintptr_t>(
+      __builtin_extract_return_addr(__builtin_return_address(0)));
+}
+
+
 char* OS::StrNDup(const char* s, intptr_t n) {
   return strndup(s, n);
 }
 
 
 intptr_t OS::StrNLen(const char* s, intptr_t n) {
   return strnlen(s, n);
 }
 
 
@@ skipping 115 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   UNIMPLEMENTED();
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_FUCHSIA)