[DevTools] Restores HeapSnapshot tests

In https://crrev.com/c/1962191 we switched off various HeapSnapshot
tests in order to complete the ES Modules migration. However, switching
these tests back on is not as trivial since they are inspector/CDP tests
that rely on the DevTools frontend JS as a dependency, and it is not
possible to load the frontend code over the file:// protocol used to
boot these tests. This CL switches the tests back on, and duplicates the
functionality from the frontend necessary to run these tests, on the
assumption that the supporting JS for these tests will need to be
managed independently of the frontend going forward.

Bug: 1110817
Change-Id: I2d0d6714e1a2b42a324dbdddda5f94ec49ee72a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2396078Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Paul Lewis <aerotwist@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807430}

third_party/blink/web_tests/TestExpectations

@@ -5893,9 +5893,6 @@ crbug.com/878878 virtual/threaded/fast/scroll-snap/snap-scrolls-visual-viewport.
 # Sheriff 2019-12-10
 crbug.com/1032451 virtual/threaded-no-composited-antialiasing/animations/stability/animation-iteration-event-destroy-renderer.html [ Pass Timeout ]
 
-# Temporarily disabled for landing changes to front_end/common in DevTools
-crbug.com/1006759 inspector-protocol/heap-profiler/heap-samples-in-snapshot.js [ Pass Failure ]
-
 # Sheriff 2019-12-13
 crbug.com/1032451 [ Win7 ] virtual/webrtc-wpt-plan-b/external/wpt/webrtc/idlharness.https.window.html [ Failure Pass ]
 crbug.com/1033852 [ Win7 ] virtual/omt-worker-fetch/external/wpt/fetch/api/idlharness.any.sharedworker.html [ Failure ]

third_party/blink/web_tests/inspector-protocol/heap-profiler/resources/heap-snapshot-common.js

@@ -6,18 +6,7 @@
 
   // This script is supposed to be evaluated in inspector-protocol/heap-profiler tests
   // and the relative paths below are relative to that location.
-  await testRunner.loadScriptModule(
-      '../../../../devtools-frontend/src/front_end/platform/utilities.js');
-  await testRunner.loadScriptModule(
-      '../../../../devtools-frontend/src/front_end/common/common-legacy.js');
-  await testRunner.loadScriptModule(
-      '../../../../devtools-frontend/src/front_end/heap_snapshot_model/HeapSnapshotModel.js');
-  await testRunner.loadScriptModule(
-      '../../../../devtools-frontend/src/front_end/heap_snapshot_worker/HeapSnapshot.js');
-  await testRunner.loadScriptModule(
-      '../../../../devtools-frontend/src/front_end/text_utils/TextUtils.js');
-  await testRunner.loadScriptModule(
-      '../../../../devtools-frontend/src/front_end/heap_snapshot_worker/HeapSnapshotLoader.js');
+  await testRunner.loadScript('./resources/HeapSnapshotLoader.js');
 
   // Expose the (de)serialize code from Common because the worker expects it on self.
   // TODO(https://crbug.com/680046) Remove the dupe code below.