Always aligns text at vertically center (Textfield, Label).

ui/gfx/font.h

Index: ui/gfx/font.h
diff --git a/ui/gfx/font.h b/ui/gfx/font.h
index 020ab64f744e1d807aaa404ddbf6bc046d218f3a..f84bfa2bf6b5e5cad3fda666240b1cbc0b989652 100644
--- a/ui/gfx/font.h
+++ b/ui/gfx/font.h
@@ -18,6 +18,15 @@ class PlatformFont;
 
 // Font provides a wrapper around an underlying font. Copy and assignment
 // operators are explicitly allowed, and cheap.
+//
+// Figure of font metrics:
+//   +--------+-------------------+------------------+
+//   |        |                   | internal leading |
+//   |        | ascent (baseline) +------------------+
+//   | height |                   | cap height       |
+//   |        |-------------------+------------------+
+//   |        | descent (height - baseline)          |
+//   +--------+--------------------------------------+
 class GFX_EXPORT Font {
  public:
   // The following constants indicate the font style.