[debug] [reland] Consistently use script from FrameMirror

src/inspector/debugger-script.js

Index: src/inspector/debugger-script.js
diff --git a/src/inspector/debugger-script.js b/src/inspector/debugger-script.js
index 98910d69df7167d0bb7e1ff8b9cd5b777cf6ec23..4746ee821ee18128c79c766fd513628d769baaa3 100644
--- a/src/inspector/debugger-script.js
+++ b/src/inspector/debugger-script.js
@@ -516,7 +516,7 @@ DebuggerScript._frameMirrorToJSCallFrame = function(frameMirror)
     {
         if (!details) {
             var scopeObjects = ensureScopeChain();
-            var script = ensureFuncMirror().script();
+            var script = frameMirror.script();

[kozy, 2016/10/13 16:06:18]

Please store scriptMirror at the beginning of this function and then use it.
Using frameMirror in lazyDetails function can be dangerous since it can be
called not on pause. I think it's a root of crash in layout tests on blink bot.

[Clemens Hammacher, 2016/10/14 10:22:50]

Done. I also removed two checks for the existence of a script, since we now
always have a Script available (I double-checked this in runtime-debug.cc).

             /** @type {!Array<Scope>} */
             var scopes = [];
             for (var i = 0; i < scopeObjects.length; ++i) {
@@ -575,7 +575,7 @@ DebuggerScript._frameMirrorToJSCallFrame = function(frameMirror)
     function ensureLocation()
     {
         if (!location) {
-            var script = ensureFuncMirror().script();
+            var script = frameMirror.script();
             if (script)
                 location = script.locationFromPosition(sourcePosition, true);
             if (!location)
@@ -620,7 +620,7 @@ DebuggerScript._frameMirrorToJSCallFrame = function(frameMirror)
      */
     function sourceID()
     {
-        var script = ensureFuncMirror().script();
+        var script = frameMirror.script();
         return script && script.id();
     }