Treat lines that cover all of a node's text similarly to an object

Currently, line ranges use a slightly different output path when they
- have start/end on the same node
 - cover the node's text i.e. are not index -1 (node
index)

This change makes it so that we don't consider the range less than a node or use
the |subNode| output path if the range surrounds the entire node's text.

Test: navigate by lines (Search+up/down) over checkboxes. Output should be the
same as Search+Left/Right.

chromevox_tests --gtest_filter=Background*.* cover caret navigation and ensuring
they still work.

Bug: 784693
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I0404e11e326116e21afc2c9131a2ceeedf21e37c
Reviewed-on: https://chromium-review.googlesource.com/798370Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521026}

chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs

@@ -1312,3 +1312,33 @@ TEST_F('BackgroundTest', 'BusyHeading', function() {
         .replay();
   });
 });
+
+TEST_F('BackgroundTest', 'NodeVsSubnode', function() {
+  var mockFeedback = this.createMockFeedback();
+  this.runWithLoadedTree(function(root) {/*!
+    <a href="#">test</a>
+  */}, function(root) {
+    var link = root.find({role: RoleType.LINK});
+    function outputLinkRange(start, end) {
+      return function() {
+        new Output().withSpeech(new cursors.Range(new cursors.Cursor(link, start),
+            new cursors.Cursor(link, end))).go();
+      };
+    }
+
+    mockFeedback.call(outputLinkRange(0, 0))
+        .expectSpeech('test', 'Link')
+        .call(outputLinkRange(0, 1))
+        .expectSpeech('t')
+        .call(outputLinkRange(1, 1))
+        .expectSpeech('test', 'Link')
+        .call(outputLinkRange(1, 2))
+        .expectSpeech('e')
+        .call(outputLinkRange(1, 3))
+        .expectNextSpeechUtteranceIsNot('Link')
+        .expectSpeech('es')
+        .call(outputLinkRange(0, 4))
+        .expectSpeech('test', 'Link')
+        .replay();
+  });
+});

chrome/browser/resources/chromeos/chromevox/cvox2/background/cursors.js

@@ -666,12 +666,15 @@ cursors.Range.prototype = {
   },
 
   /**
-   * Returns true if this range covers a single node's text content or less.
+   * Returns true if this range covers less than a node.
    * @return {boolean}
    */
   isSubNode: function() {
-    return this.start.node === this.end.node && this.start.index > -1 &&
-        this.end.index > -1;
+    var startIndex = this.start.index;
+    var endIndex = this.end.index;
+    return this.start.node === this.end.node && startIndex != -1 &&
+        endIndex != -1 && startIndex != endIndex &&
+        (startIndex != 0 || endIndex != this.start.getText().length);
   },
 
   /**