[omnibox bookmarks] Make short symbols match beginning of words

Currently, a symbol (that a user might enter in the Omnibox) that is
very short (e.g. 1 char) will not be allowed to match the beginning of
a word. This CL flips that match behavior to allow a partial match,
but only when a flag is set. We intend to measure and make sure that
suggestion quality doesn't degrade.

TBR: [email protected]
Bug: 925815
Change-Id: If279d0add5015a11d7528710a8cde020fba5cdef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1488615
Reviewed-by: Kevin Bailey <[email protected]>
Reviewed-by: Justin Donnelly <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Commit-Queue: Kevin Bailey <[email protected]>
Cr-Commit-Position: refs/heads/master@{#656034}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 304cd9e..050b71e 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -815,6 +815,9 @@
 extern const char kOmniboxRichEntitySuggestionsName[];
 extern const char kOmniboxRichEntitySuggestionsDescription[];
 
+extern const char kOmniboxShortBookmarkSuggestionsName[];
+extern const char kOmniboxShortBookmarkSuggestionsDescription[];
+
 extern const char kOmniboxSpareRendererName[];
 extern const char kOmniboxSpareRendererDescription[];