DevTools: Add runtime functions that allow specific file requests

This CL adds the following functions:

* Runtime.getResourceURL: returns the request URL given resource name and
request base URL (e.g. devtools://devtools/bundle/ or
devtools://devtools/remote/serve_file/@010ddcfda246975d194964ccf20038ebbdec6084/)
* (Runtime) module: return Runtime.Module object given module name
* (Runtime.Module) fetchResource: make a request to load a script of the given
name in the current module. This is in the Runtime.Module class so that the
request can be adjusted based on if the module is remote or not.

We can leverage these functions to request specific files. I'm planning to
use them to request the appropriate locale file for lighthouse in the
audits worker, e.g.
`await self.runtime.module('audits_worker').fetchResource('lighthouse/locales/zh.json')`.

Bug: 941561
Change-Id: Ib5c7bfdc46bef7d98533c89b12c7d365d4a26dfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1784981Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Paul Irish <paulirish@chromium.org>
Commit-Queue: Mandy Chen <mandy.chen@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#697719}

third_party/blink/renderer/devtools/front_end/Runtime.js

@@ -149,6 +149,20 @@ var Runtime = class {  // eslint-disable-line
     return normalizedPath;
   }
 
+  /**
+   * @param {string} scriptName
+   * @param {string=} base
+   * @return {string}
+   */
+  static getResourceURL(scriptName, base) {
+    const sourceURL = (base || self._importScriptPathPrefix) + scriptName;
+    const schemaIndex = sourceURL.indexOf('://') + 3;
+    let pathIndex = sourceURL.indexOf('/', schemaIndex);
+    if (pathIndex === -1)
+      pathIndex = sourceURL.length;
+    return sourceURL.substring(0, pathIndex) + Runtime.normalizePath(sourceURL.substring(pathIndex));
+  }
+
   /**
    * @param {!Array.<string>} scriptNames
    * @param {string=} base
@@ -163,13 +177,7 @@ var Runtime = class {  // eslint-disable-line
     let scriptToEval = 0;
     for (let i = 0; i < scriptNames.length; ++i) {
       const scriptName = scriptNames[i];
-      let sourceURL = (base || self._importScriptPathPrefix) + scriptName;
-
-      const schemaIndex = sourceURL.indexOf('://') + 3;
-      let pathIndex = sourceURL.indexOf('/', schemaIndex);
-      if (pathIndex === -1)
-        pathIndex = sourceURL.length;
-      sourceURL = sourceURL.substring(0, pathIndex) + Runtime.normalizePath(sourceURL.substring(pathIndex));
+      const sourceURL = Runtime.getResourceURL(scriptName, base);
 
       if (_loadedScripts[sourceURL])
         continue;
@@ -391,6 +399,14 @@ var Runtime = class {  // eslint-disable-line
       Runtime._remoteBase += 'debug/';
   }
 
+  /**
+   * @param {string} moduleName
+   * @return {!Runtime.Module}
+   */
+  module(moduleName) {
+    return this._modulesMap[moduleName];
+  }
+
   /**
    * @param {!Runtime.ModuleDescriptor} descriptor
    */
@@ -790,6 +806,16 @@ Runtime.Module = class {
     return !Runtime.queryParam('debugFrontend') && this._descriptor.remote && Runtime._remoteBase || undefined;
   }
 
+  /**
+   * @param {string} resourceName
+   * @return {!Promise.<string>}
+   */
+  fetchResource(resourceName) {
+    const base = this._remoteBase();
+    const sourceURL = Runtime.getResourceURL(this._modularizeURL(resourceName), base);
+    return base ? Runtime.loadResourcePromiseWithFallback(sourceURL) : Runtime.loadResourcePromise(sourceURL);
+  }
+
   /**
    * @param {string} value
    * @return {string}