Avoid int coercion of box-shadow args

third_party/WebKit/Source/platform/graphics/DrawLooperBuilder.cpp

Index: third_party/WebKit/Source/platform/graphics/DrawLooperBuilder.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/DrawLooperBuilder.cpp b/third_party/WebKit/Source/platform/graphics/DrawLooperBuilder.cpp
index fc1c64856c8bcca7584a393d12c788f95f820a97..7c16dc9a90c3e788fe36440b562ef4d324e9cdf5 100644
--- a/third_party/WebKit/Source/platform/graphics/DrawLooperBuilder.cpp
+++ b/third_party/WebKit/Source/platform/graphics/DrawLooperBuilder.cpp
@@ -67,9 +67,7 @@ void DrawLooperBuilder::addUnmodifiedContent()
 void DrawLooperBuilder::addShadow(const FloatSize& offset, float blur, const Color& color,
     ShadowTransformMode shadowTransformMode, ShadowAlphaMode shadowAlphaMode)
 {
-    // Negative blurs are not allowed, so just pin the value to 0
-    if (blur < 0)
-        blur = 0;
+    ASSERT(blur >= 0);

[Justin Novosad, 2015/11/16 23:07:19]

Did a bit of digging... I find it hard to prove with 100% certanty, just by
reading the code, that blur is always pre-clamped.  Are you sure about this
ASSERT? 
SkBlurMaskFilter::Create already knows to hanlde blurs <= 0 by not blurring.

[f(malita), 2015/11/17 13:55:23]

I can't spot the place where it gets sanitized either, but negative values are
not allowed for blur radius, per spec:
http://www.w3.org/TR/css3-background/#box-shadow

Both the test and my manual fiddling cannot produce a negative value at this
stage - so I presume the style engine must clamp it (or default to 0 for inval
negative values).
Yeah, but skBlurRadiusToSigma ASSERTS on negative values - see linked bug.

[Justin Novosad, 2015/11/17 14:19:03]

This code is also used by 2d canvas, svg, and the values may be the result of an
animation curve interpolation. Canvas and animation curves are clamping, I
checked. Anyways, I think this is Okay.

 
     // Detect when there's no effective shadow.
     if (!color.alpha())