Treat <table> widths of 0 as auto.

third_party/WebKit/Source/core/layout/LayoutTable.cpp

Index: third_party/WebKit/Source/core/layout/LayoutTable.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTable.cpp b/third_party/WebKit/Source/core/layout/LayoutTable.cpp
index ae3e5c0d4391dc2582f8f17f34240e74cad2ecce..c61d0bef9600995c74882a0d6e3d181840186eb5 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTable.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTable.cpp
@@ -271,8 +271,12 @@ void LayoutTable::updateLogicalWidth()
     bool hasPerpendicularContainingBlock = cb->style()->isHorizontalWritingMode() != style()->isHorizontalWritingMode();
     LayoutUnit containerWidthInInlineDirection = hasPerpendicularContainingBlock ? perpendicularContainingBlockLogicalHeight() : availableLogicalWidth;
 
+    ASSERT(!style()->logicalWidth().isNegative());
+    if (style()->logicalWidth().isSpecified() && style()->logicalWidth().isZero()) {
+        mutableStyle()->setLogicalWidth(Length());

[dgrogan, 2016/02/09 03:27:19]

I'm not sure how much of a no-no this is, to mutate the style during layout.
Perhaps I should instead modify whatever transforms a negative specified width
into auto to do the same for a zero specified width? Do you know where that is?
I've not been able to find it yet.

[mstensho (USE GERRIT), 2016/02/09 10:52:45]

I think this is bad. We should really leave computed style alone. Negative
width? Do we have those? The parser shouldn't have allowed that, since it would
be a spec violation.

Non-positive widths as in zero, sure - but negative widths???

[dgrogan, 2016/02/10 02:47:56]

No, we don't have negative widths, which is why I added the ASSERT. Some code
below checks for negative widths though...

+    }
     Length styleLogicalWidth = style()->logicalWidth();
-    if ((styleLogicalWidth.isSpecified() && styleLogicalWidth.isPositive()) || styleLogicalWidth.isIntrinsic()) {

[dgrogan, 2016/02/09 03:27:19]

With the above change this clause is always true.

+    if (styleLogicalWidth.isSpecified() || styleLogicalWidth.isIntrinsic()) {
         setLogicalWidth(convertStyleLogicalWidthToComputedWidth(styleLogicalWidth, containerWidthInInlineDirection));
     } else {
         // Subtract out any fixed margins from our available width for auto width tables.