[CI] Use color enumeration in SVGPaintContext::PaintForLayoutObject

The code in its current form gives the impression that there's a
dependency on the initial value of the 'fill' property, while all we
really want to say here is 'black'. Use a more direct approach.

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ib75ba965c585771e9a009f91f0055a592a37c1b0
Reviewed-on: https://chromium-review.googlesource.com/926845Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#537861}

third_party/WebKit/Source/core/paint/SVGPaintContext.cpp

@@ -248,7 +248,7 @@ bool SVGPaintContext::PaintForLayoutObject(
   if (paint_info.IsRenderingClipPathAsMaskImage()) {
     if (resource_mode == kApplyToStrokeMode)
       return false;
-    flags.setColor(SVGComputedStyle::InitialFillPaintColor().Rgb());
+    flags.setColor(SK_ColorBLACK);
     flags.setShader(nullptr);
     return true;
   }