Rename command installProviderExtension to launchProviderExtension

crrev.com/555016 changed the C++ browser-test-side code to use the name
LaunchExtension(), rather than InstallExtension(). Change the test code
JS command similarly, use launchProviderExtension.

Also make launchProviderExtension a separate getSetupSteps step because
chrome test.sendMessage always has a reply. We should await it and then
do the next step: setup that next step to call setupAndWaitUntilReady()
as before.

Covered by existing tests: Provider/FileManagerBrowserTest/Test.*

Bug: 833834,668680
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I0cffa47ae94e46699fd1e92d69dea946686d6ad1
Reviewed-on: https://chromium-review.googlesource.com/1036747Reviewed-by: Stuart Langley <slangley@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555205}

chrome/browser/chromeos/file_manager/file_manager_browsertest_base.cc

@@ -761,7 +761,7 @@ void FileManagerBrowserTestBase::OnCommand(const std::string& name,
     return;
   }
 
-  if (name == "installProviderExtension") {
+  if (name == "launchProviderExtension") {
     std::string manifest;
     ASSERT_TRUE(value.GetString("manifest", &manifest));
     LaunchExtension(base::FilePath(FILE_PATH_LITERAL(

ui/file_manager/integration_tests/file_manager/providers.js

@@ -10,8 +10,8 @@ var appId;
 
 /**
  * Returns steps for initializing test cases.
- * @param {string} manifest Name of the manifest to load for the testing
- *     provider extension.
+ * @param {string} manifest The manifest name of testing provider extension
+ *     to launch for the test case.
  * @return {!Array<function>}
  */
 function getSetupSteps(manifest) {
@@ -19,9 +19,11 @@ function getSetupSteps(manifest) {
     function() {
       chrome.test.sendMessage(
           JSON.stringify({
-            name: 'installProviderExtension',
+            name: 'launchProviderExtension',
             manifest: manifest
-          }));
+          }), this.next);
+    },
+    function() {
       setupAndWaitUntilReady(null, RootPath.DOWNLOADS, this.next);
     },
     function(results) {