Gracefully handle unloaded scripts

If a script is unloaded between the collection of an allocation and the
tranlation of an allocation profile, the profiler will segfault. With
this change, we report unloaded scripts as having no line number,column
number, or name.

R=ofrobots@google.com
BUG=

Review URL: https://codereview.chromium.org/1846723002

Cr-Commit-Position: refs/heads/master@{#35147}

src/profiler/sampling-heap-profiler.cc

@@ -200,7 +200,8 @@ v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
   int column = v8::AllocationProfile::kNoColumnNumberInfo;
   std::vector<v8::AllocationProfile::Allocation> allocations;
   allocations.reserve(node->allocations_.size());
-  if (node->script_id_ != v8::UnboundScript::kNoScriptId) {
+  if (node->script_id_ != v8::UnboundScript::kNoScriptId &&
+      scripts.find(node->script_id_) != scripts.end()) {
     // Cannot use std::map<T>::at because it is not available on android.
     auto non_const_scripts = const_cast<std::map<int, Script*>&>(scripts);
     Script* script = non_const_scripts[node->script_id_];

test/cctest/test-heap-profiler.cc

@@ -2875,7 +2875,6 @@ static const v8::AllocationProfile::Node* FindAllocationProfileNode(
   return node;
 }
 
-
 TEST(SamplingHeapProfiler) {
   v8::HandleScope scope(v8::Isolate::GetCurrent());
   LocalContext env;
@@ -2988,6 +2987,23 @@ TEST(SamplingHeapProfiler) {
 
     heap_profiler->StopSamplingHeapProfiler();
   }
+
+  // A test case with scripts unloaded before profile gathered
+  {
+    heap_profiler->StartSamplingHeapProfiler(64);
+    CompileRun(
+        "for (var i = 0; i < 1024; i++) {\n"
+        "  eval(\"new Array(100)\");\n"
+        "}\n");
+
+    CcTest::heap()->CollectAllGarbage();
+
+    v8::base::SmartPointer<v8::AllocationProfile> profile(
+        heap_profiler->GetAllocationProfile());
+    CHECK(!profile.is_empty());
+
+    heap_profiler->StopSamplingHeapProfiler();
+  }
 }