Make bigger string size in RenderTextHarfBuzz.

ui/gfx/render_text_harfbuzz.cc

Index: ui/gfx/render_text_harfbuzz.cc
diff --git a/ui/gfx/render_text_harfbuzz.cc b/ui/gfx/render_text_harfbuzz.cc
index 0580abe3375e09bddae437c08a958ee6a7d16977..8af8c1f7ad41ee764bf5a8d91cd37686dd229595 100644
--- a/ui/gfx/render_text_harfbuzz.cc
+++ b/ui/gfx/render_text_harfbuzz.cc
@@ -233,6 +233,8 @@ class HarfBuzzLineBreaker {
         run_list_(run_list),
         text_x_(0),
         line_x_(0),
+        max_top_(0),
+        max_bottom_(0),
         max_descent_(0),
         max_ascent_(0) {
     DCHECK_EQ(multiline_, (words_ != nullptr));
@@ -256,10 +258,12 @@ class HarfBuzzLineBreaker {
   // Finishes line breaking and outputs the results. Can be called at most once.
   void Finalize(std::vector<internal::Line>* lines, SizeF* size) {
     DCHECK(!lines_.empty());
+    float trailing_height = std::max(0.f, max_bottom_ - max_descent_);
     // Add an empty line to finish the line size calculation and remove it.
     AdvanceLine();
     lines_.pop_back();
     *size = total_size_;
+    size->Enlarge(0, trailing_height);
     lines->swap(lines_);
   }
 
@@ -384,10 +388,18 @@ class HarfBuzzLineBreaker {
       line->size.set_height(std::max(min_height_, max_descent_ + max_ascent_));
       line->baseline =
           std::max(min_baseline_, SkScalarRoundToInt(max_ascent_));
-      line->preceding_heights = std::ceil(total_size_.height());
-      total_size_.set_height(total_size_.height() + line->size.height());
+      if (line == &lines_.front()) {

[msw, 2015/02/24 23:31:35]

Why does only the first line add the extra height between |max_top_| and
|max_ascent_|? Why is that different than your change to make all lines add the
extra height between |max_bottom_| and |max_descent_|? Add an explanatory
comment in one or both places.

[Jun Mukai, 2015/02/25 23:49:19]

Comments added.  Our code base seems to assume line height for the height
between ascent and descent, therefore changing this to the height between top
and bottom would make extra space between lines.

+        line->preceding_heights =
+            std::ceil(std::max(0.f, max_top_ - max_ascent_));
+        total_size_.set_height(line->preceding_heights + line->size.height());
+      } else {
+        line->preceding_heights = std::ceil(total_size_.height());
+        total_size_.set_height(total_size_.height() + line->size.height());
+      }
       total_size_.set_width(std::max(total_size_.width(), line->size.width()));
     }
+    max_top_ = 0;
+    max_bottom_ = 0;
     max_descent_ = 0;
     max_ascent_ = 0;
     line_x_ = 0;
@@ -422,8 +434,10 @@ class HarfBuzzLineBreaker {
 
     line->size.set_width(line->size.width() + width);
     max_descent_ = std::max(max_descent_, metrics.fDescent);
-    // fAscent is always negative.
+    max_bottom_ = std::max(max_bottom_, metrics.fBottom);
+    // fAscent and fTop are always negative.
     max_ascent_ = std::max(max_ascent_, -metrics.fAscent);
+    max_top_ = std::max(max_top_, -metrics.fTop);
 
     if (run.is_rtl) {
       rtl_segments_.push_back(
@@ -452,6 +466,8 @@ class HarfBuzzLineBreaker {
   SkScalar text_x_;
   SkScalar line_x_;
 
+  float max_top_;
+  float max_bottom_;
   float max_descent_;
   float max_ascent_;