DevTools: reenable last-execution-context.js test

This test should not rely on stability of V8 sort algorithm.

TBR=dgozman@chromium.org

Bug: chromium:855582
Change-Id: Ia1678da6d4ba8a04d5b7135f34e1748632414720
Reviewed-on: https://chromium-review.googlesource.com/1242042Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593780}

third_party/WebKit/LayoutTests/TestExpectations

@@ -1741,9 +1741,6 @@ crbug.com/591099 virtual/layout_ng_experimental/external/wpt/css/css-flexbox/ord
 crbug.com/591099 virtual/layout_ng_experimental/external/wpt/css/css-flexbox/order/order-with-row-reverse.html [ Failure ]
 # ====== LayoutNG-only failures until here ======
 
-# V8 will break this and needs rebaseline.
-crbug.com/855582 http/tests/devtools/sources/debugger-ui/last-execution-context.js [ Failure Pass ]
-
 ### sheriff 2018-05-28
 crbug.com/840238 http/tests/devtools/elements/shadow/shadow-distribution.js [ Failure ]
 

third_party/WebKit/LayoutTests/http/tests/devtools/sources/debugger-ui/last-execution-context.js

@@ -81,7 +81,7 @@
 
   TestRunner.addResult('');
   TestRunner.addResult('User selected content script');
-  context.setFlavor(SDK.ExecutionContext, pageRuntimeModel.executionContexts()[2]);
+  context.setFlavor(SDK.ExecutionContext, pageRuntimeModel.executionContexts().find(context => context.id === 'cs1'));
 
   TestRunner.addResult('');
   TestRunner.addResult('Switching to sw target');
@@ -93,7 +93,7 @@
 
   TestRunner.addResult('');
   TestRunner.addResult('User selected iframe1');
-  context.setFlavor(SDK.ExecutionContext, pageRuntimeModel.executionContexts()[0]);
+  context.setFlavor(SDK.ExecutionContext, pageRuntimeModel.executionContexts().find(context => context.id === 'if1'));
 
   TestRunner.addResult('');
   TestRunner.addResult('Switching to sw target');