inspector: introduce V8Inspector::contextById(contextId)

This is a pre-requisite for https://chromium-review.googlesource.com/c/chromium/src/+/1134430

R=kozy

Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;luci.chromium.try:linux_chromium_rel_ng;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ic437eaffd0870e1ce6b16e4992e9232515e091ec
Reviewed-on: https://chromium-review.googlesource.com/1173718Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55131}

include/v8-inspector.h

@@ -245,6 +245,7 @@ class V8_EXPORT V8Inspector {
   virtual void contextCreated(const V8ContextInfo&) = 0;
   virtual void contextDestroyed(v8::Local<v8::Context>) = 0;
   virtual void resetContextGroup(int contextGroupId) = 0;
+  virtual v8::MaybeLocal<v8::Context> contextById(int contextId) = 0;
 
   // Various instrumentation.
   virtual void idleStarted() = 0;

src/inspector/v8-inspector-impl.cc

@@ -188,6 +188,11 @@ InspectedContext* V8InspectorImpl::getContext(int contextId) const {
   return getContext(contextGroupId(contextId), contextId);
 }
 
+v8::MaybeLocal<v8::Context> V8InspectorImpl::contextById(int contextId) {
+  InspectedContext* context = getContext(contextId);
+  return context ? context->context() : v8::MaybeLocal<v8::Context>();
+}
+
 void V8InspectorImpl::contextCreated(const V8ContextInfo& info) {
   int contextId = ++m_lastContextId;
   InspectedContext* context = new InspectedContext(this, info, contextId);

src/inspector/v8-inspector-impl.h

@@ -78,6 +78,7 @@ class V8InspectorImpl : public V8Inspector {
                                               const StringView& state) override;
   void contextCreated(const V8ContextInfo&) override;
   void contextDestroyed(v8::Local<v8::Context>) override;
+  v8::MaybeLocal<v8::Context> contextById(int contextId) override;
   void contextCollected(int contextGroupId, int contextId);
   void resetContextGroup(int contextGroupId) override;
   void idleStarted() override;