Remove views::Label::SetDisabledColor(). Replace with typography colors.

ui/views/style/typography.cc

Index: ui/views/style/typography.cc
diff --git a/ui/views/style/typography.cc b/ui/views/style/typography.cc
index 034d56da29063b6bfd1a8b9ebfe50864d814b493..9be18583c3527bca07ed04dc502a8e9a4b11c69f 100644
--- a/ui/views/style/typography.cc
+++ b/ui/views/style/typography.cc
@@ -5,6 +5,7 @@
 #include "ui/views/style/typography.h"
 
 #include "base/logging.h"
+#include "ui/native_theme/native_theme.h"
 #include "ui/views/layout/layout_provider.h"
 #include "ui/views/style/typography_provider.h"
 
@@ -26,10 +27,13 @@ const gfx::FontList& GetFont(int text_context, int text_style) {
                                                                 text_style);
 }
 
-SkColor GetColor(int text_context, int text_style) {
+SkColor GetColor(int text_context,
+                 int text_style,
+                 const ui::NativeTheme* native_theme) {
   ValidateContextAndStyle(text_context, text_style);
-  return LayoutProvider::Get()->GetTypographyProvider().GetColor(text_context,
-                                                                 text_style);
+  DCHECK(native_theme);

[Peter Kasting, 2017/06/01 04:55:58]

Why not just pass in by const ref then, as typography_provider.h does?

[tapted, 2017/06/01 11:22:18]

Then all the callsites need an extra character in front of GetNativeTheme() to
dereference it :).. 

I also considered that in future we could reasonably pass in nullptr and have
GetColor(), here, fall back to ui::NativeTheme::GetInstanceForNativeUi().
Currently those null checks are in view.cc or widget.cc, but it's possible
something will want a color when neither of those are around, like a Painter or
a Background.

(But I wanted it to be clear to the providers that they never have to consider a
null nativetheme, hence const-ref for those)

[Peter Kasting, 2017/06/01 19:08:01]

Hmm.  That sounds like a "maybe it would be useful to pass null someday" rather
than an "in the future I'll be changing these to pass null".

In keeping with the last sentence in
http://google.github.io/styleguide/cppguide.html#Reference_Arguments , I'd
probably pass const ref and add the '*' at all callsites.  But I will leave the
final decision to you.

[tapted, 2017/06/02 01:29:15]

I feel a '*' at callsites is more cognitive load for the callers than the issue
raised in that sentence. i.e. forcing callers to dereference requires them to
think whether they should DCHECK or check for null or provide a fallback. So..
really I think GetNativeTheme() should return const-ref rather than a pointer.
But that's a bigger refactor and raises questions on android where it currently
can return null.

+  return LayoutProvider::Get()->GetTypographyProvider().GetColor(
+      text_context, text_style, *native_theme);
 }
 
 int GetLineHeight(int text_context, int text_style) {