Enable CSS hyphens property on stable

This patch enables CSS hyphens property on stable.

Following values are valid at this point:
  Android/Mac: manual | none | auto
  Other platforms: manual | none

BUG=605840

Review-Url: https://codereview.chromium.org/2342553003
Cr-Commit-Position: refs/heads/master@{#419461}

third_party/WebKit/LayoutTests/virtual/stable/webexposed/css-properties-as-js-properties-expected.txt

@@ -132,6 +132,7 @@ fontWeight
 getPropertyPriority
 getPropertyValue
 height
+hyphens
 imageRendering
 isolation
 item

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

@@ -59,7 +59,7 @@ CSSContainment status=stable
 CSSFontDisplay status=experimental
 CSSFontSizeAdjust status=experimental
 CSSGridLayout status=experimental, settable_from_internals=True
-CSSHyphens status=experimental
+CSSHyphens status=stable
 CSSInBodyDoesNotBlockPaint status=experimental
 CSSIndependentTransformProperties status=experimental
 CSSMaskSourceType status=experimental