DevTools: allow ShiftTab to focus away from CodeMirror

CodeMirror text editors try to reduce indentation on 'Shift+Tab'.
However, this consumes the key event, preventing focus from leaving,
even if nothing changed.

This CL allows focus to leave when we are sure that no indentation
should change. Shift+Tab can now move focus from Console prompt to
toolbar and from SourceFrame's editor to the Sources TabbedPane.

Bug: none
Change-Id: I3660a48fe1c30a0972e2908514ee44fba7a51132
Reviewed-on: https://chromium-review.googlesource.com/1142519
Commit-Queue: Erik Luo <luoe@chromium.org>
Reviewed-by: Andrey Lushnikov <lushnikov@chromium.org>
Reviewed-by: Joel Einbinder <einbinder@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577406}

third_party/blink/renderer/devtools/front_end/text_editor/CodeMirrorTextEditor.js

@@ -74,7 +74,7 @@ TextEditor.CodeMirrorTextEditor = class extends UI.VBox {
       'Delete': 'delCharAfter',
       'Backspace': 'delCharBefore',
       'Tab': 'defaultTab',
-      'Shift-Tab': 'indentLess',
+      'Shift-Tab': 'indentLessOrPass',
       'Enter': 'newlineAndIndent',
       'Ctrl-Space': 'autocomplete',
       'Esc': 'dismiss',
@@ -1324,6 +1324,20 @@ CodeMirror.commands.selectCamelLeft = TextEditor.CodeMirrorTextEditor.moveCamelL
 CodeMirror.commands.moveCamelRight = TextEditor.CodeMirrorTextEditor.moveCamelRightCommand.bind(null, false);
 CodeMirror.commands.selectCamelRight = TextEditor.CodeMirrorTextEditor.moveCamelRightCommand.bind(null, true);
 
+/**
+ * @param {!CodeMirror} codeMirror
+ * @return {!Object|undefined}
+ */
+CodeMirror.commands.indentLessOrPass = function(codeMirror) {
+  const selections = codeMirror.listSelections();
+  if (selections.length === 1) {
+    const range = TextEditor.CodeMirrorUtils.toRange(selections[0].anchor, selections[0].head);
+    if (range.isEmpty() && !/^\s/.test(codeMirror.getLine(range.startLine)))
+      return CodeMirror.Pass;
+  }
+  codeMirror.execCommand('indentLess');
+};
+
 /**
  * @param {!CodeMirror} codeMirror
  */
@@ -1371,6 +1385,7 @@ CodeMirror.commands.redoAndReveal = function(codemirror) {
 };
 
 /**
+ * @param {!CodeMirror} codemirror
  * @return {!Object|undefined}
  */
 CodeMirror.commands.dismiss = function(codemirror) {
@@ -1389,6 +1404,7 @@ CodeMirror.commands.dismiss = function(codemirror) {
 };
 
 /**
+ * @param {!CodeMirror} codemirror
  * @return {!Object|undefined}
  */
 CodeMirror.commands.goSmartPageUp = function(codemirror) {
@@ -1398,6 +1414,7 @@ CodeMirror.commands.goSmartPageUp = function(codemirror) {
 };
 
 /**
+ * @param {!CodeMirror} codemirror
  * @return {!Object|undefined}
  */
 CodeMirror.commands.goSmartPageDown = function(codemirror) {