Tiny fix: initialize TickSample::frames_count with 0.

src/platform.h

 // Copyright 2006-2008 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 475 matching lines @@
 // ----------------------------------------------------------------------------
 // Sampler
 //
 // A sampler periodically samples the state of the VM and optionally
 // (if used for profiling) the program counter and stack pointer for
 // the thread that created it.
 
 // TickSample captures the information collected for each sample.
 class TickSample {
  public:
-  TickSample() : pc(0), sp(0), fp(0), state(OTHER) {}
+  TickSample() : pc(0), sp(0), fp(0), state(OTHER), frames_count(0) {}
   uintptr_t pc;  // Instruction pointer.
   uintptr_t sp;  // Stack pointer.
   uintptr_t fp;  // Frame pointer.
   StateTag state;   // The state of the VM.
   static const int kMaxFramesCount = 100;
   EmbeddedVector<Address, kMaxFramesCount> stack;  // Call stack.
   int frames_count;  // Number of captured frames.
 };
 
 class Sampler {
@@ skipping 24 matching lines @@
   bool active_;
   PlatformData* data_;  // Platform specific data.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_