Rename TagContext -> TagMap

Author: mayurkale22

packages/opencensus-instrumentation-http/src/http.ts

@@ -219,7 +219,7 @@ export class HttpPlugin extends BasePlugin {
             const host = headers.host || 'localhost';
             const userAgent =
                 (headers['user-agent'] || headers['User-Agent']) as string;
-            const tags = HttpPlugin.getTagContext(headers) || new TagMap();
+            const tags = HttpPlugin.getTagMap(headers) || new TagMap();
 
             rootSpan.addAttribute(
                 HttpPlugin.ATTRIBUTE_HTTP_HOST,
@@ -538,7 +538,7 @@ export class HttpPlugin extends BasePlugin {
    * @param headers The incoming HTTP header object from which TagMap should be
    *     retrieved.
    */
-  static getTagContext(headers: IncomingHttpHeaders): TagMap|null {
+  static getTagMap(headers: IncomingHttpHeaders): TagMap|null {
     const contextValue = (headers[CORRELATION_CONTEXT.toLocaleLowerCase()] ||
                           headers[CORRELATION_CONTEXT]) as string;
     // Entry doesn't exist.