Fix CPU profiler crash in start / stop sequence when non-existent name is passed

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 8316079a8d09ab427056e15e6ac7d04696182fae..1d1aa812bc09e32ab00fe37f4086250ca1dc055d 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -542,13 +542,6 @@ CpuProfile* CpuProfilesCollection::StopProfiling(int security_token_id,
 }
 
 
-CpuProfile* CpuProfilesCollection::StopProfiling(int security_token_id,
-                                                 String* title,
-                                                 double actual_sampling_rate) {
-  return StopProfiling(security_token_id, GetName(title), actual_sampling_rate);
-}
-
-
 CpuProfile* CpuProfilesCollection::GetProfile(int security_token_id,
                                               unsigned uid) {
   HashMap::Entry* entry = profiles_uids_.Lookup(reinterpret_cast<void*>(uid),
@@ -574,6 +567,15 @@ CpuProfile* CpuProfilesCollection::GetProfile(int security_token_id,
 }
 
 
+bool CpuProfilesCollection::IsLastProfile(const char* title) {
+  // Called from VM thread, and only it can mutate the list,
+  // so no locking is needed here.
+  if (current_profiles_.length() != 1) return false;
+  return StrLength(title) == 0
+      || strcmp(current_profiles_[0]->title(), title) == 0;
+}
+
+
 int CpuProfilesCollection::TokenToIndex(int security_token_id) {
   ASSERT(TokenEnumerator::kNoSecurityToken == -1);
   return security_token_id + 1;  // kNoSecurityToken -> 0, 0 -> 1, ...