Make sure line widths in the range of 0px and 1px are rounded up to 1px for visibility.

third_party/WebKit/Source/core/css/resolver/AnimatedStyleBuilder.cpp

Index: third_party/WebKit/Source/core/css/resolver/AnimatedStyleBuilder.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/AnimatedStyleBuilder.cpp b/third_party/WebKit/Source/core/css/resolver/AnimatedStyleBuilder.cpp
index f1760d084e5beb529ad8c7beb818961d3d64636a..dde8e17743f67a8c20026d210dda62fe83e42953 100644
--- a/third_party/WebKit/Source/core/css/resolver/AnimatedStyleBuilder.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/AnimatedStyleBuilder.cpp
@@ -99,6 +99,13 @@ template<typename T> T animatableValueClampTo(const AnimatableValue* value, T mi
     return clampTo<T>(roundForImpreciseConversion<T>(toAnimatableDouble(value)->toDouble()), min, max);
 }
 
+template<typename T> T animatableLineWidthClamp(const AnimatableValue* value)
+{
+    double doubleValue = toAnimatableDouble(value)->toDouble();
+    // This matches StyleBuilderConverter::convertLineWidth().
+    return (doubleValue > 0 && doubleValue < 1) ? 1 : animatableValueClampTo<T>(value);
+}
+
 LengthBox animatableValueToLengthBox(const AnimatableValue* value, const StyleResolverState& state, ValueRange range = ValueRangeAll)
 {
     const AnimatableLengthBox* animatableLengthBox = toAnimatableLengthBox(value);
@@ -315,7 +322,7 @@ void AnimatedStyleBuilder::applyProperty(CSSPropertyID property, StyleResolverSt
         style->setBorderBottomRightRadius(animatableValueToLengthSize(value, state, ValueRangeNonNegative));
         return;
     case CSSPropertyBorderBottomWidth:
-        style->setBorderBottomWidth(animatableValueClampTo<unsigned>(value));
+        style->setBorderBottomWidth(animatableLineWidthClamp<unsigned>(value));
         return;
     case CSSPropertyBorderImageOutset:
         style->setBorderImageOutset(animatableValueToBorderImageLengthBox(value, state));
@@ -335,14 +342,14 @@ void AnimatedStyleBuilder::applyProperty(CSSPropertyID property, StyleResolverSt
         style->setVisitedLinkBorderLeftColor(toAnimatableColor(value)->visitedLinkColor());
         return;
     case CSSPropertyBorderLeftWidth:
-        style->setBorderLeftWidth(animatableValueClampTo<unsigned>(value));
+        style->setBorderLeftWidth(animatableLineWidthClamp<unsigned>(value));
         return;
     case CSSPropertyBorderRightColor:
         style->setBorderRightColor(toAnimatableColor(value)->color());
         style->setVisitedLinkBorderRightColor(toAnimatableColor(value)->visitedLinkColor());
         return;
     case CSSPropertyBorderRightWidth:
-        style->setBorderRightWidth(animatableValueClampTo<unsigned>(value));
+        style->setBorderRightWidth(animatableLineWidthClamp<unsigned>(value));
         return;
     case CSSPropertyBorderTopColor:
         style->setBorderTopColor(toAnimatableColor(value)->color());
@@ -355,7 +362,7 @@ void AnimatedStyleBuilder::applyProperty(CSSPropertyID property, StyleResolverSt
         style->setBorderTopRightRadius(animatableValueToLengthSize(value, state, ValueRangeNonNegative));
         return;
     case CSSPropertyBorderTopWidth:
-        style->setBorderTopWidth(animatableValueClampTo<unsigned>(value));
+        style->setBorderTopWidth(animatableLineWidthClamp<unsigned>(value));
         return;
     case CSSPropertyBottom:
         style->setBottom(animatableValueToLength(value, state));
@@ -470,7 +477,7 @@ void AnimatedStyleBuilder::applyProperty(CSSPropertyID property, StyleResolverSt
         style->setOutlineOffset(animatableValueClampTo<int>(value));
         return;
     case CSSPropertyOutlineWidth:
-        style->setOutlineWidth(animatableValueClampTo<unsigned short>(value));
+        style->setOutlineWidth(animatableLineWidthClamp<unsigned short>(value));
         return;
     case CSSPropertyPaddingBottom:
         style->setPaddingBottom(animatableValueToLength(value, state, ValueRangeNonNegative));
@@ -551,7 +558,7 @@ void AnimatedStyleBuilder::applyProperty(CSSPropertyID property, StyleResolverSt
         style->setColumnWidth(clampTo(toAnimatableDouble(value)->toDouble(), std::numeric_limits<float>::epsilon()));
         return;
     case CSSPropertyWebkitColumnRuleWidth:
-        style->setColumnRuleWidth(clampTo<unsigned short>(toAnimatableDouble(value)->toDouble()));
+        style->setColumnRuleWidth(animatableLineWidthClamp<unsigned short>(value));
         return;
     case CSSPropertyWebkitFilter:
         style->setFilter(toAnimatableFilterOperations(value)->operations());