[LayoutNG] Fix max-content size when floats are outside of content box

This patch fixes max-content size when the line has floats
outside of its content box.

In such case, ComputeContentSize computes a negative value
for |floats_inline_size|. Such |floats_inline_size| should
not affect max-content size.

Bug: 636993
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Ie3076c1a135a8bf00a264f7275abb19ef1392864
Reviewed-on: https://chromium-review.googlesource.com/1113094Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570350}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-features=LayoutNG

@@ -417,7 +417,6 @@ crbug.com/591099 fast/css/getComputedStyle/computed-style-percentage-top-with-po
 crbug.com/591099 fast/css/getComputedStyle/getComputedStyle-margin-auto.html [ Failure ]
 crbug.com/591099 fast/css/getComputedStyle/getComputedStyle-margin-percentage.html [ Failure ]
 crbug.com/591099 fast/css/import_with_baseurl.html [ Failure ]
-crbug.com/591099 fast/css/negative-text-indent-in-inline-block.html [ Failure ]
 crbug.com/591099 fast/css/opacity-float.html [ Pass ]
 crbug.com/591099 fast/css/outline-narrowLine.html [ Failure ]
 crbug.com/591099 fast/css/text-overflow-ellipsis-vertical-hittest.html [ Failure ]

third_party/blink/renderer/core/layout/ng/ng_block_layout_algorithm.cc

@@ -266,10 +266,16 @@ base::Optional<MinMaxSize> NGBlockLayoutAlgorithm::ComputeMinMaxSize(
       // A float adds to its inline size to the current "line". The new max
       // inline contribution is just the sum of all the floats on that "line".
       LayoutUnit float_inline_size = child_sizes.max_size + margins.InlineSum();
-      if (child_style.Floating() == EFloat::kLeft)
-        float_left_inline_size += float_inline_size;
-      else
-        float_right_inline_size += float_inline_size;
+
+      // float_inline_size is negative when the float is completely outside of
+      // the content area, by e.g., negative margins. Such floats do not affect
+      // the content size.
+      if (float_inline_size > 0) {
+        if (child_style.Floating() == EFloat::kLeft)
+          float_left_inline_size += float_inline_size;
+        else
+          float_right_inline_size += float_inline_size;
+      }
 
       max_inline_contribution =
           float_left_inline_size + float_right_inline_size;