[HeapMojo] Deprecate HeapMojoWrapperMode::kWithoutContextObserver for DevToolsFrontendImpl.

[purpose]
The HeapMojoWrapperMode::kWithoutContextObserver was a HeapMojoWrapper's "safe mofe" to keep the existing behavior during the COVID-19 code freeze.

The mojo objects on DevToolsFrontendImpl must outlive the ExecutionContext of LocalFrame, so it should not be associated with the ExecutionContext of LocalFrame.

Bug: 1049056
Change-Id: I9c0b469ca206005a00a921838d24569c80f598a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2291911Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Minoru Chikamune <chikamune@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833156}

third_party/blink/renderer/controller/dev_tools_frontend_impl.cc

@@ -65,9 +65,7 @@ const char DevToolsFrontendImpl::kSupplementName[] = "DevToolsFrontendImpl";
 DevToolsFrontendImpl::DevToolsFrontendImpl(
     LocalFrame& frame,
     mojo::PendingAssociatedReceiver<mojom::blink::DevToolsFrontend> receiver)
-    : Supplement<LocalFrame>(frame),
-      host_(frame.DomWindow()),
-      receiver_(this, frame.DomWindow()) {
+    : Supplement<LocalFrame>(frame) {
   receiver_.Bind(std::move(receiver),
                  frame.GetTaskRunner(TaskType::kMiscPlatformAPI));
 }

third_party/blink/renderer/controller/dev_tools_frontend_impl.h

@@ -37,7 +37,6 @@
 #include "third_party/blink/renderer/platform/heap/handle.h"
 #include "third_party/blink/renderer/platform/mojo/heap_mojo_associated_receiver.h"
 #include "third_party/blink/renderer/platform/mojo/heap_mojo_associated_remote.h"
-#include "third_party/blink/renderer/platform/mojo/heap_mojo_wrapper_mode.h"
 #include "third_party/blink/renderer/platform/supplementable.h"
 #include "third_party/blink/renderer/platform/wtf/hash_map.h"
 #include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
@@ -84,13 +83,14 @@ class DevToolsFrontendImpl final
 
   Member<DevToolsHost> devtools_host_;
   String api_script_;
-  HeapMojoAssociatedRemote<mojom::blink::DevToolsFrontendHost,
-                           HeapMojoWrapperMode::kForceWithoutContextObserver>
-      host_;
+  // The host_ must outlive the ExecutionContext of LocalFrame, so it should not
+  // be associated with the ExecutionContext of LocalFrame.
+  HeapMojoAssociatedRemote<mojom::blink::DevToolsFrontendHost> host_{nullptr};
+  // The receiver_ must outlive the ExecutionContext of LocalFrame, so it should
+  // not be associated with the ExecutionContext of LocalFrame.
   HeapMojoAssociatedReceiver<mojom::blink::DevToolsFrontend,
-                             DevToolsFrontendImpl,
-                             HeapMojoWrapperMode::kForceWithoutContextObserver>
-      receiver_;
+                             DevToolsFrontendImpl>
+      receiver_{this, nullptr};
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsFrontendImpl);
 };