style: Split apply_declarations into its own file, and without mako.

All that font code thrown out in the middle was making me mad.

There should be no change in behavior from this patch.

I ran rustfmt on the code but I corrected manually the following:

  https://github.com/rust-lang-nursery/rustfmt/issues/3025

Differential Revision: https://phabricator.services.mozilla.com/D5970

components/style/values/specified/color.rs

@@ -317,12 +317,12 @@ impl Color {
             .map_err(|()| location.new_custom_error(StyleParseErrorKind::UnspecifiedError))
     }
 
-    /// Returns false if the color is completely transparent, and
-    /// true otherwise.
-    pub fn is_non_transparent(&self) -> bool {
+    /// Returns true if the color is completely transparent, and false
+    /// otherwise.
+    pub fn is_transparent(&self) -> bool {
         match *self {
-            Color::Numeric { ref parsed, .. } => parsed.alpha != 0,
-            _ => true,
+            Color::Numeric { ref parsed, .. } => parsed.alpha == 0,
+            _ => false,
         }
     }
 }