Clean-up: Renames gfx::Font's methods and removes its obsolete methods.

Applies the same renaming as http://crrev.com/142523003 and also removes obsolete methods.

Renamed methods:
- DeriveFont(size_delta, style) => Derive(size_delta, style)

Removed methods:
- DeriveFont(size_delta)
- GetAverageCharacterWidth()
  # Use GetExpectedTextWidth(1) instead.
- GetStringWidth(text)
  # Use gfx::GetStringWidth(text, font_list) instead.

BUG=265485
TEST=Run ui_unittests, views_unittests.

Review URL: https://codereview.chromium.org/138013004

git-svn-id: http://src.chromium.org/svn/trunk/src/build@251028 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/pylib/gtest/filter/ui_unittests_disabled

@@ -21,12 +21,11 @@ FontListTest.Fonts_FromFontWithNonNormalStyle
 FontListTest.Fonts_GetHeight_GetBaseline
 FontListTest.Fonts_GetStyle
 FontTest.Ascent
-FontTest.AvgCharWidth
 FontTest.AvgWidths
 FontTest.CapHeight
 FontTest.GetActualFontNameForTesting
 FontTest.Height
 FontTest.LoadArial
 FontTest.LoadArialBold
-FontTest.Widths
 ResourceBundleTest.DelegateGetFontList
+TextUtilsTest.GetStringWidth