devtools: Reenable inspector-backend-commands.js http test.

The test was disabled in commit 46327ef9 ("Temporarily disable web tests
that use the legacy Protocol global") but was never enabled again.

Adapt to changes that have happened in devtools-frontend since then:
* Rename Protocol to ProtocolClient
  <https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2107558>
* Adjust -expected.txt and essentially revert commit 424f76fd ("update
  test for devtools inspector backend")
  <https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2193586>
* Remove the last argument to the registerCommand() call.
  <https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2230524>

Bug: 1011811
Change-Id: I7f311536f6c25577f86e8906723f61a6c9b0ad96
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2575016
Auto-Submit: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834596}

third_party/blink/web_tests/TestExpectations

@@ -1738,7 +1738,6 @@ crbug.com/400841 media/video-canvas-draw.html [ Failure ]
 crbug.com/1032016 http/tests/devtools/sources/debugger-breakpoints/breakpoints-ui-shifted-breakpoint.js [ Pass Failure Timeout ]
 
 # Renaming front_end/protocol to front_end/protocol_client requires a 3-way change. Temporarliy disable web tests that use |Protocol|
-crbug.com/1011811 http/tests/devtools/inspector-backend-commands.js [ Pass Failure ]
 crbug.com/1011811 http/tests/devtools/report-protocol-errors.js [ Pass Failure ]
 crbug.com/1047760 http/tests/devtools/screen-orientation-override.js [ Pass Failure Timeout ]
 crbug.com/1011811 http/tests/devtools/elements/styles-1/cached-sync-computed-styles.js [ Pass Failure ]

third_party/blink/web_tests/http/tests/devtools/inspector-backend-commands-expected.txt

 Tests correctness of promisified protocol commands.
 
 error: Request Profiler.commandError failed. {"message":"this is the error message"}
-commandError: catch result: {"message":"this is the error message"}
+commandError: then result: null
 commandArgs0: then result: undefined
 error: Protocol Error: Extra 1 arguments in a call to method 'Profiler.commandArgs0'.
 commandArgs0: then result: null

third_party/blink/web_tests/http/tests/devtools/inspector-backend-commands.js

@@ -5,7 +5,7 @@
 (async function() {
   TestRunner.addResult(`Tests correctness of promisified protocol commands.\n`);
 
-  Protocol.test.suppressRequestErrors = false;
+  ProtocolClient.test.suppressRequestErrors = false;
   function dumpArgument(name, value) {
     TestRunner.addResult(name + ' result: ' + (typeof value === 'string' ? value : JSON.stringify(value)));
   }
@@ -47,20 +47,20 @@
     }]
   };
   // The protocol definition above is not used, but is left as a reference for commands below.
-  Protocol.inspectorBackend.registerCommand('Profiler.commandArgs0', [], [], false);
-  Protocol.inspectorBackend.registerCommand(
-      'Profiler.commandArgs1Rets0', [{'name': 'arg1', 'type': 'number', 'optional': false}], [], false);
-  Protocol.inspectorBackend.registerCommand(
-      'Profiler.commandArgs1Rets1', [{'name': 'arg1', 'type': 'object', 'optional': false}], ['arg1'], false);
-  Protocol.inspectorBackend.registerCommand(
+  ProtocolClient.inspectorBackend.registerCommand('Profiler.commandArgs0', [], []);
+  ProtocolClient.inspectorBackend.registerCommand(
+      'Profiler.commandArgs1Rets0', [{'name': 'arg1', 'type': 'number', 'optional': false}], []);
+  ProtocolClient.inspectorBackend.registerCommand(
+      'Profiler.commandArgs1Rets1', [{'name': 'arg1', 'type': 'object', 'optional': false}], ['arg1']);
+  ProtocolClient.inspectorBackend.registerCommand(
       'Profiler.commandArgs3Rets3',
       [
         {'name': 'arg1', 'type': 'object', 'optional': false}, {'name': 'arg2', 'type': 'number', 'optional': true},
         {'name': 'arg3', 'type': 'string', 'optional': true}
       ],
-      ['arg1', 'arg2', 'arg3'], false);
-  Protocol.inspectorBackend.registerCommand(
-      'Profiler.commandError', [{'name': 'error', 'type': 'object', 'optional': false}], [], false);
+      ['arg1', 'arg2', 'arg3']);
+  ProtocolClient.inspectorBackend.registerCommand(
+      'Profiler.commandError', [{'name': 'error', 'type': 'object', 'optional': false}], []);
 
   var sendMessageToBackendOriginal = InspectorFrontendHost.sendMessageToBackend;
   InspectorFrontendHost.sendMessageToBackend = sendMessageToBackendLoopback;