Make styled-label trimming less agressive, allowing whitespace

ui/views/controls/styled_label.cc

Index: ui/views/controls/styled_label.cc
diff --git a/ui/views/controls/styled_label.cc b/ui/views/controls/styled_label.cc
index 1b4cf1c93aaa038342e0949d9ce75ff1a78478d3..604c95fad213ad6b111cf11f700831c0cf798d8a 100644
--- a/ui/views/controls/styled_label.cc
+++ b/ui/views/controls/styled_label.cc
@@ -259,11 +259,17 @@ gfx::Size StyledLabel::CalculateAndDoLayout(int width, bool dry_run) {
   // Iterate over the text, creating a bunch of labels and links and laying them
   // out in the appropriate positions.
   while (!remaining_string.empty()) {
-    // Don't put whitespace at beginning of a line with an exception for the
-    // first line (so the text's leading whitespace is respected).
     if (x == 0 && line > 0) {
-      base::TrimWhitespace(remaining_string, base::TRIM_LEADING,
-                           &remaining_string);
+      if (remaining_string.front() == L'\n') {
+        // Wrapped to the next line on \n, remove it. Other whitespace,
+        // eg, spaces to indent next line, are preserved.
+        remaining_string.erase(0, 1);
+      } else {
+        // Wrapped on whitespace character or characters in the middle of the
+        // line - none of them are needed at the beginning of the next line.
+        base::TrimWhitespace(remaining_string, base::TRIM_LEADING,
+                             &remaining_string);
+      }
     }
 
     gfx::Range range(gfx::Range::InvalidRange());
@@ -293,19 +299,22 @@ gfx::Size StyledLabel::CalculateAndDoLayout(int width, bool dry_run) {
     if (substrings.empty() || substrings[0].empty()) {
       // Nothing fits on this line. Start a new line.
       // If x is 0, first line may have leading whitespace that doesn't fit in a
-      // single line, so try trimming those. Otherwise there is no room for
-      // anything; abort.
+      // single line, so try trimming those. When first remaining char is \n,
+      // otput it as an empty line.
+      // Otherwise there is no room for anything; abort.

[Evan Stade, 2016/12/09 18:41:58]

When I rewrite this portion of the function (L299-319) to this[1], all tests
still pass. Is this a valid rewrite or is the test coverage incomplete?

[1]
    if (substrings.empty())
      break;

    if (substrings[0].empty()) {
      x = 0;
      ++line;
      continue;
    }

       if (x == 0) {
         if (line == 0) {
           base::TrimWhitespace(remaining_string, base::TRIM_LEADING,
                                &remaining_string);
           continue;
+        } else if (remaining_string.empty() ||
+                   remaining_string.front() != L'\n') {
+          break;
         }
-        break;
       }
 
       x = 0;
-      line++;
+      ++line;
       continue;
     }
 
@@ -320,7 +329,7 @@ gfx::Size StyledLabel::CalculateAndDoLayout(int width, bool dry_run) {
         // If the chunk should not be wrapped, try to fit it entirely on the
         // next line.
         x = 0;
-        line++;
+        ++line;
         continue;
       }