DevTools: introduce new cm_headless module to fix formatter_worker deps.

third_party/WebKit/Source/devtools/BUILD.gn

Index: third_party/WebKit/Source/devtools/BUILD.gn
diff --git a/third_party/WebKit/Source/devtools/BUILD.gn b/third_party/WebKit/Source/devtools/BUILD.gn
index 44a82662455f452855f4b9eba6b82eafb6ce166b..64c64425a9f515a74679e244da3ca22e773c4905 100644
--- a/third_party/WebKit/Source/devtools/BUILD.gn
+++ b/third_party/WebKit/Source/devtools/BUILD.gn
@@ -77,9 +77,6 @@ all_devtools_files = [
   "front_end/cm/codemirror.js",
   "front_end/cm/comment.js",
   "front_end/cm/css.js",
-  "front_end/cm/css.js",
-  "front_end/cm/headlesscodemirror.js",
-  "front_end/cm/headlesscodemirror.js",
   "front_end/cm/htmlembedded.js",
   "front_end/cm/htmlmixed.js",
   "front_end/cm/javascript.js",
@@ -89,7 +86,8 @@ all_devtools_files = [
   "front_end/cm/overlay.js",
   "front_end/cm/simple.js",
   "front_end/cm/xml.js",
-  "front_end/cm/xml.js",
+  "front_end/cm_headless/headlesscodemirror.js",
+  "front_end/cm_headless/module.json",
   "front_end/common/CharacterIdMap.js",
   "front_end/common/Color.js",
   "front_end/common/Console.js",
@@ -111,11 +109,9 @@ all_devtools_files = [
   "front_end/common/TextDictionary.js",
   "front_end/common/TextRange.js",
   "front_end/common/TextUtils.js",
-  "front_end/common/TextUtils.js",
   "front_end/common/Throttler.js",
   "front_end/common/Trie.js",
   "front_end/common/UIString.js",
-  "front_end/common/UIString.js",
   "front_end/common/Worker.js",
   "front_end/components_lazy/CookiesTable.js",
   "front_end/components_lazy/filmStripDialog.css",
@@ -227,7 +223,6 @@ all_devtools_files = [
   "front_end/formatter_worker.js",
   "front_end/formatter_worker.json",
   "front_end/formatter_worker/acorn/acorn.js",
-  "front_end/formatter_worker/acorn/acorn.js",
   "front_end/formatter_worker/AcornTokenizer.js",
   "front_end/formatter_worker/CSSFormatter.js",
   "front_end/formatter_worker/CSSRuleParser.js",
@@ -326,15 +321,12 @@ all_devtools_files = [
   "front_end/persistence/PersistenceUtils.js",
   "front_end/platform/module.json",
   "front_end/platform/utilities.js",
-  "front_end/platform/utilities.js",
-  "front_end/platform/utilities.js",
   "front_end/profiler/BottomUpProfileDataGrid.js",
   "front_end/profiler/CPUProfileFlameChart.js",
   "front_end/profiler/CPUProfileView.js",
   "front_end/profiler/heapProfiler.css",
   "front_end/profiler/HeapProfileView.js",
   "front_end/profiler/HeapSnapshotCommon.js",
-  "front_end/profiler/HeapSnapshotCommon.js",
   "front_end/profiler/HeapSnapshotDataGrids.js",
   "front_end/profiler/HeapSnapshotGridNodes.js",
   "front_end/profiler/HeapSnapshotProxy.js",