Fix libdl dependency on Android and remove librt hack.

src/perf-jit.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_PERF_JIT_H_
 #define V8_PERF_JIT_H_
 
 #include "src/v8.h"
 
 namespace v8 {
 namespace internal {
 
-// TODO(jarin) For now, we disable perf integration on Android because of a
-// build problem - when building the snapshot with AOSP, librt is not
-// available, so we cannot use the clock_gettime function. To fix this, we
-// should thread through the V8_LIBRT_NOT_AVAILABLE flag here and only disable
-// the perf integration when this flag is present (the perf integration is not
-// needed when generating snapshot, so it is fine to ifdef it away).
-
 #if V8_OS_LINUX
 
 // Linux perf tool logging support
 class PerfJitLogger : public CodeEventLogger {
  public:
   PerfJitLogger();
   virtual ~PerfJitLogger();
 
   virtual void CodeMoveEvent(Address from, Address to);
   virtual void CodeDeleteEvent(Address from);
@@ skipping 58 matching lines @@
   virtual void LogRecordedBuffer(Code* code, SharedFunctionInfo* shared,
                                  const char* name, int length) {
     UNIMPLEMENTED();
   }
 };
 
 #endif  // V8_OS_LINUX
 }
 }  // namespace v8::internal
 #endif