Restore a collapsed leading space of text used for line break

When a text is wrapped during layout, the leading space of the
text can be collapsed and a line break is inserted instead of
the space. In this case, we need to restore the collapsed space
when we copy the text.

This CL can handle the following case:
<div style="width: 2em;"><b><i>foo</i></b> bar</div>

BUG=318925
TEST=editing/pasteboard/restore-collapsed-space-for-copy.html

Review-Url: https://codereview.chromium.org/2320533002
Cr-Commit-Position: refs/heads/master@{#417155}

third_party/WebKit/LayoutTests/editing/pasteboard/preserve-trailing-space.html → third_party/WebKit/LayoutTests/editing/pasteboard/restore-collapsed-space-for-copy.html

@@ -10,7 +10,7 @@ test(() => assert_selection(
     selection.document.execCommand('paste');
   },
   '<div style="width: 10em;">Copy this area <a href="http://foo/">AVeryLongWordThatWillWrap</a></div><div contenteditable>Copy this area <a href="http://foo/">AVeryLongWordThatWillWrap|</a></div>'),
-  '1. Restore the collapsed space');
+  '1. Restore the collapsed trailing space');
 
 test(() => assert_selection(
   '<div style="width: 2em;"><b><i>foo </i></b>bar</div><div contenteditable>|</div>',
@@ -19,7 +19,16 @@ test(() => assert_selection(
     selection.document.execCommand('paste');
   },
  '<div style="width: 2em;"><b><i>foo </i></b>bar</div><div contenteditable><b><i>foo </i></b>bar|</div>'),
-  '2. Restore the collapsed space');
+  '2. Restore the collapsed trailing space');
+
+test(() => assert_selection(
+  '<div style="width: 2em;"><b><i>foo</i></b> bar</div><div contenteditable>|</div>',
+  selection => {
+    selection.setClipboardData('<b><i>foo</i></b> bar');
+    selection.document.execCommand('paste');
+  },
+  '<div style="width: 2em;"><b><i>foo</i></b> bar</div><div contenteditable><b><i>foo</i></b> bar|</div>'),
+  '3. Restore the collapsed leading space');
 
 test(() => assert_selection(
   '<div style="width: 2em;">작은홍띠점박이푸른부전나비</div><div contenteditable>|</div>',
@@ -28,7 +37,7 @@ test(() => assert_selection(
     selection.document.execCommand('paste');
   },
  '<div style="width: 2em;">작은홍띠점박이푸른부전나비</div><div contenteditable>작은홍띠점박이푸른부전나비|</div>'),
-  '3. Space should not be added for CJK');
+  '4. Space should not be added for CJK');
 
 test(() => assert_selection(
   '<div style="width: 2em; word-break: break-all">Pneumonoultramicroscopicsilicovolcanoconiosis</div><div contenteditable>|</div>',
@@ -37,5 +46,5 @@ test(() => assert_selection(
     selection.document.execCommand('paste');
   },
  '<div style="width: 2em; word-break: break-all">Pneumonoultramicroscopicsilicovolcanoconiosis</div><div contenteditable>Pneumonoultramicroscopicsilicovolcanoconiosis|</div>'),
-  '4. Space should not be added for CSS word-break: break-all');
+  '5. Space should not be added for CSS word-break: break-all');
 </script>

third_party/WebKit/Source/core/editing/iterators/TextIterator.cpp

@@ -611,12 +611,22 @@ void TextIteratorAlgorithm<Strategy>::handleTextBox()
                     size_t subrunEnd = str.find('\n', runStart);
                     if (subrunEnd == kNotFound || subrunEnd > runEnd) {
                         subrunEnd = runEnd;
-                        // Restore the collapsed trailing space for copy & paste.
+                        // Restore the collapsed space for copy & paste.
                         // See http://crbug.com/318925
+                        // For trailing space.
                         if (!nextTextBox && m_textBox->root().nextRootBox() && m_textBox->root().lastChild() == m_textBox) {
                             if (str.endsWith(' ') && subrunEnd == str.length() - 1 && str[subrunEnd - 1] != ' ')
                                 ++subrunEnd;
                         }
+                        // For leading space.
+                        if (m_textBox->root().prevRootBox() && m_textBox->root().firstChild() == m_textBox) {
+                            InlineBox* lastChildOfPrevRoot = m_textBox->root().prevRootBox()->lastChild();
+                            if (!lastChildOfPrevRoot->isText() && !lastChildOfPrevRoot->getLineLayoutItem().isBR()
+                                && !lastChildOfPrevRoot->isInlineFlowBox()) {
+                                if (runStart > 0 && str[0] == ' ')
+                                    --runStart;
+                            }
+                        }
                     }
 
                     m_offset = subrunEnd;