Add initialization for has_external_callback field.

It looks like we initialize TickSample values twice in some
situations, but I will fix this in a separate change list.

R=sgjesse@chromium.org
BUG=1292
TEST=none

Review URL: http://codereview.chromium.org/6756031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7434 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/cpu-profiler-inl.h

@@ -70,6 +70,7 @@ TickSampleEventRecord* TickSampleEventRecord::init(void* value) {
   // Init the required fields only.
   result->sample.pc = NULL;
   result->sample.frames_count = 0;
+  result->sample.has_external_callback = false;
   return result;
 }
 

src/cpu-profiler.cc

@@ -187,6 +187,7 @@ void ProfilerEventsProcessor::AddCurrentStack() {
   sample->state = Isolate::Current()->current_vm_state();
   sample->pc = reinterpret_cast<Address>(sample);  // Not NULL.
   sample->tos = NULL;
+  sample->has_external_callback = false;
   sample->frames_count = 0;
   for (StackTraceFrameIterator it;
        !it.done() && sample->frames_count < TickSample::kMaxFramesCount;

src/log.cc

@@ -150,6 +150,7 @@ void StackTracer::Trace(Isolate* isolate, TickSample* sample) {
 
   sample->tos = NULL;
   sample->frames_count = 0;
+  sample->has_external_callback = false;
 
   // Avoid collecting traces while doing GC.
   if (sample->state == GC) return;

src/platform.h

@@ -596,7 +596,8 @@ class TickSample {
         sp(NULL),
         fp(NULL),
         tos(NULL),
-        frames_count(0) {}
+        frames_count(0),
+        has_external_callback(false) {}
   StateTag state;  // The state of the VM.
   Address pc;      // Instruction pointer.
   Address sp;      // Stack pointer.

tools/tickprocessor.js

@@ -345,7 +345,6 @@ TickProcessor.prototype.includeTick = function(vmState) {
   return this.stateFilter_ == null || this.stateFilter_ == vmState;
 };
 
-
 TickProcessor.prototype.processTick = function(pc,
                                                sp,
                                                is_external_callback,
@@ -361,8 +360,10 @@ TickProcessor.prototype.processTick = function(pc,
   if (is_external_callback) {
     // Don't use PC when in external callback code, as it can point
     // inside callback's code, and we will erroneously report
-    // that a callback calls itself.
-    pc = 0;
+    // that a callback calls itself. Instead we use tos_or_external_callback,
+    // as simply resetting PC will produce unaccounted ticks.
+    pc = tos_or_external_callback;
+    tos_or_external_callback = 0;
   } else if (tos_or_external_callback) {
     // Find out, if top of stack was pointing inside a JS function
     // meaning that we have encountered a frameless invocation.