Revert of RELEASE_ASSERT if last resort fallback font cannot be loaded....

Revert of RELEASE_ASSERT if last resort fallback font cannot be loaded. (patchset #1 id:1 of https://codereview.chromium.org/641763003/)

Reason for revert:
Reverting per request.
https://code.google.com/p/chromium/issues/detail?id=421370#c11

Original issue's description:
> RELEASE_ASSERT if last resort fallback font cannot be loaded.
> 
> This will help confirm the suspicion that a number of ClusterFuzz reports
> from constructTextRun are a result of this failing. There's probably nothing
> useful that can be done with a font that lacks any font data anyhow.
> 
> BUG=421370
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=183470

TBR=eae@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=421370,423643

Review URL: https://codereview.chromium.org/659073002

git-svn-id: svn://svn.chromium.org/blink/trunk@183815 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/fonts/FontFallbackList.cpp

@@ -144,7 +144,7 @@ const SimpleFontData* FontFallbackList::determinePrimarySimpleFontData(const Fon
                 return fontData->fontDataForCharacter(space);
 
             SimpleFontData* lastResortFallback = FontCache::fontCache()->getLastResortFallbackFont(fontDescription).get();
-            RELEASE_ASSERT(lastResortFallback);
+            ASSERT(lastResortFallback);
             return lastResortFallback;
         }