[cpu-profiler] Fix string length calculation for GetConsName

Currently, GetConsName incorrectly includes the null terminator as part
of the length used in the string's hash. Exclude this to be consistent
with GetCopy, GetName, etc. and permit coalescing.

Bug: v8:0
Change-Id: I1e8a4eb7055637f3ed178014725b44e84d7788b6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2578192Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Andrew Comminos <acomminos@fb.com>
Cr-Commit-Position: refs/heads/master@{#71667}

src/profiler/strings-storage.cc

@@ -101,7 +101,7 @@ const char* StringsStorage::GetConsName(const char* prefix, Name name) {
     char* cons_result = NewArray<char>(cons_length);
     snprintf(cons_result, cons_length, "%s%s", prefix, data.get());
 
-    return AddOrDisposeString(cons_result, cons_length);
+    return AddOrDisposeString(cons_result, cons_length - 1);
   } else if (name.IsSymbol()) {
     return "<symbol>";
   }

test/unittests/profiler/strings-storage-unittest.cc

@@ -157,5 +157,17 @@ TEST_F(StringsStorageWithIsolate, InvalidRelease) {
 #endif  // DEBUG
 }
 
+TEST_F(StringsStorageWithIsolate, CopyAndConsShareStorage) {
+  StringsStorage storage;
+
+  Handle<String> str = isolate()->factory()->NewStringFromAsciiChecked("foo");
+
+  const char* copy_str = storage.GetCopy("get foo");
+  const char* cons_str = storage.GetConsName("get ", *str);
+
+  CHECK_EQ(storage.GetStringCountForTesting(), 1);
+  CHECK_EQ(copy_str, cons_str);
+}
+
 }  // namespace internal
 }  // namespace v8