Fix usages of location symbol

This is required for landing
https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2450036

R=szuend@chromium.org

Bug: 1011811
Change-Id: Iff89f391e7bfa238c4eaeeb5e1ddc4efad19bd05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461267
Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Auto-Submit: Tim van der Lippe <tvanderlippe@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815090}

third_party/blink/web_tests/http/tests/devtools/persistence/persistence-move-breakpoints-on-reload.js

@@ -56,7 +56,7 @@
       return TestRunner.textContentWithLineBreaks(pane._emptyElement);
     var entries = Array.from(pane.contentElement.querySelectorAll('.breakpoint-entry'));
     for (var entry of entries) {
-      var uiLocation = entry[Sources.JavaScriptBreakpointsSidebarPane._locationSymbol];
+      var uiLocation = Sources.JavaScriptBreakpointsSidebarPane.retrieveLocationForElement(entry)
       TestRunner.addResult('    ' + uiLocation.uiSourceCode.url() + ':' + uiLocation.lineNumber);
     }
   }

third_party/blink/web_tests/http/tests/devtools/persistence/persistence-move-breakpoints.js

@@ -58,7 +58,7 @@
       return TestRunner.textContentWithLineBreaks(pane._emptyElement);
     var entries = Array.from(pane.contentElement.querySelectorAll('.breakpoint-entry'));
     for (var entry of entries) {
-      var uiLocation = entry[Sources.JavaScriptBreakpointsSidebarPane._locationSymbol];
+      var uiLocation = Sources.JavaScriptBreakpointsSidebarPane.retrieveLocationForElement(entry);
       TestRunner.addResult('    ' + uiLocation.uiSourceCode.url() + ':' + uiLocation.lineNumber);
     }
   }

third_party/blink/web_tests/http/tests/devtools/sources/debugger-breakpoints/debugger-reload-breakpoints-with-source-maps.js

@@ -44,8 +44,7 @@
             .contentElement;
     var entries = Array.from(paneElement.querySelectorAll('.breakpoint-entry'));
     for (var entry of entries) {
-      var uiLocation =
-          entry[Sources.JavaScriptBreakpointsSidebarPane._locationSymbol];
+      var uiLocation = Sources.JavaScriptBreakpointsSidebarPane.retrieveLocationForElement(entry);
       if (Bindings.CompilerScriptMapping.StubProjectID ===
           uiLocation.uiSourceCode.project().id())
         return SourcesTestRunner.waitBreakpointSidebarPane().then(