Add textfield internal padding from FocusableBorder.

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index bedee3a1c0c8cabcece0a1f5d192c79e9f5d5191..9e424894920cbe789852651e152caea3f2544397 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -238,6 +238,7 @@ int GetViewsCommand(const ui::TextEditCommandAuraLinux& command, bool rtl) {
 
 // static
 const char Textfield::kViewClassName[] = "Textfield";
+const int Textfield::kTextPadding = 3;
 
 // static
 size_t Textfield::GetCaretBlinkMs() {
@@ -555,7 +556,8 @@ int Textfield::GetBaseline() const {
 }
 
 gfx::Size Textfield::GetPreferredSize() const {
-  const gfx::Insets& insets = GetInsets();
+  gfx::Insets insets = GetInsets();
+  insets += gfx::Insets(kTextPadding, kTextPadding, kTextPadding, kTextPadding);
   return gfx::Size(GetFontList().GetExpectedTextWidth(default_width_in_chars_) +
                    insets.width(), GetFontList().GetHeight() + insets.height());
 }
@@ -919,7 +921,13 @@ void Textfield::GetAccessibleState(ui::AXViewState* state) {
 }
 
 void Textfield::OnBoundsChanged(const gfx::Rect& previous_bounds) {
-  GetRenderText()->SetDisplayRect(GetContentsBounds());
+  // Allow the text to paint over vertical padding, but not horizontal padding.
+  // kTextPadding was previously unused FocusableBorder inset padding, now that
+  // space is reserved for excessively tall text from unforseen fallback fonts.
+  // This is better than clipping text, shrinking text or painting over borders.

[Peter Kasting, 2014/08/30 00:46:43]

Hmm, I'd really rather not talk about "previously", as over time it becomes more
confusing than meaningful.  How about this comment:

The default kTextPadding value is chosen so there's a reasonable amount of
whitespace on all sides of the user's default font.  Because some fallback fonts
may be taller than the default font, we allow fonts to paint over the vertical
part of this whitespace area.  There are a number of possible alternate
behaviors, such as shrinking fallback fonts more, or dynamically enlarging the
control, but this allows the most reasonable combination of "default font looks
good", "fallback fonts are large enough to be readable", and "controls don't
change size dynamically (surprising users)".

[msw, 2014/09/04 01:25:51]

I revised the comment.

+  gfx::Rect bounds = GetContentsBounds();
+  bounds.Inset(kTextPadding, 0);
+  GetRenderText()->SetDisplayRect(bounds);
   OnCaretBoundsChanged();
 }