String::NewExternal should not crash the renderer.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index f1d81ddd5fefa38f3704d11a6c1c7478f97e46c5..bda34bdfacacbb369f5e8db2b18d03c6f38b1ec7 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -5483,21 +5483,15 @@ Local<String> v8::String::Concat(Handle<String> left, Handle<String> right) {
 }
 
 
-static i::Handle<i::String> NewExternalStringHandle(
-    i::Isolate* isolate,
-    v8::String::ExternalStringResource* resource) {
-  // We do not expect this to fail. Change this if it does.
-  return isolate->factory()->NewExternalStringFromTwoByte(
-      resource).ToHandleChecked();
+static i::MaybeHandle<i::String> NewExternalStringHandle(
+    i::Isolate* isolate, v8::String::ExternalStringResource* resource) {
+  return isolate->factory()->NewExternalStringFromTwoByte(resource);
 }
 
 
-static i::Handle<i::String> NewExternalOneByteStringHandle(
+static i::MaybeHandle<i::String> NewExternalOneByteStringHandle(
     i::Isolate* isolate, v8::String::ExternalOneByteStringResource* resource) {
-  // We do not expect this to fail. Change this if it does.
-  return isolate->factory()
-      ->NewExternalStringFromOneByte(resource)
-      .ToHandleChecked();
+  return isolate->factory()->NewExternalStringFromOneByte(resource);
 }
 
 
@@ -5508,9 +5502,13 @@ Local<String> v8::String::NewExternal(
   LOG_API(i_isolate, "String::NewExternal");
   ENTER_V8(i_isolate);
   CHECK(resource && resource->data());
-  i::Handle<i::String> result = NewExternalStringHandle(i_isolate, resource);
-  i_isolate->heap()->external_string_table()->AddString(*result);
-  return Utils::ToLocal(result);
+  EXCEPTION_PREAMBLE(i_isolate);
+  i::Handle<i::String> string;
+  has_pending_exception =
+      !NewExternalStringHandle(i_isolate, resource).ToHandle(&string);
+  EXCEPTION_BAILOUT_CHECK(i_isolate, Local<String>());
+  i_isolate->heap()->external_string_table()->AddString(*string);
+  return Utils::ToLocal(string);
 }
 
 
@@ -5546,10 +5544,13 @@ Local<String> v8::String::NewExternal(
   LOG_API(i_isolate, "String::NewExternal");
   ENTER_V8(i_isolate);
   CHECK(resource && resource->data());
-  i::Handle<i::String> result =
-      NewExternalOneByteStringHandle(i_isolate, resource);
-  i_isolate->heap()->external_string_table()->AddString(*result);
-  return Utils::ToLocal(result);
+  EXCEPTION_PREAMBLE(i_isolate);
+  i::Handle<i::String> string;
+  has_pending_exception =
+      !NewExternalOneByteStringHandle(i_isolate, resource).ToHandle(&string);
+  EXCEPTION_BAILOUT_CHECK(i_isolate, Local<String>());
+  i_isolate->heap()->external_string_table()->AddString(*string);
+  return Utils::ToLocal(string);
 }