Make NGFragmentItem::GetWritingMode() to work other than text

This patch changes |NGFragmentItem::GetWritingMode()| to work other than text
because it is independent from text and value of CSS property.

Note: This patch fixes 17 web_test crashes.

Bug: 982194
Change-Id: I9f5fdaddb12f3d88b50a1f6c87b026b505ce8ea7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1943497
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720139}

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.h

@@ -246,7 +246,6 @@ class CORE_EXPORT NGFragmentItem : public DisplayItemClient {
   }
 
   WritingMode GetWritingMode() const {
-    DCHECK(Type() == kText || Type() == kGeneratedText) << this;
     return Style().GetWritingMode();
   }