[inspector] Store interger in context embedder data instead of a string.

src/inspector/inspected-context.h

Index: src/inspector/inspected-context.h
diff --git a/src/inspector/inspected-context.h b/src/inspector/inspected-context.h
index f31eb76419e4fd14f28d6dba3cbd9922d75dab11..f8d97e9b940acf0951e2a882faa788d862003116 100644
--- a/src/inspector/inspected-context.h
+++ b/src/inspector/inspected-context.h
@@ -21,6 +21,8 @@ class InspectedContext {
  public:
   ~InspectedContext();
 
+  static int contextId(v8::Local<v8::Context>);
+
   v8::Local<v8::Context> context() const;
   int contextId() const { return m_contextId; }
   int contextGroupId() const { return m_contextGroupId; }