Reland "Disable Instant Extended limit by default for Android."

This reverts commit 74affe26.

Reason for revert: we're now ready to enable this feature by default.

Original change's description:
> Revert "Disable Instant Extended limit by default for Android."
>
> This reverts commit 3b71610c.
>
> Reason for revert: we will be doing staged rollout. this cl would go live may 19, which is too early.
>
> Original change's description:
> > Disable Instant Extended limit by default for Android.
> >
> > This change effectively increases number of search results
> > on Android devices from default (3).
> >
> > Bug: 964049
> > Change-Id: I46887f88e3f76801d24f7dfdf928397e6a3ae66f
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2132858
> > Reviewed-by: Tommy Li <tommycli@chromium.org>
> > Commit-Queue: Ender <ender@google.com>
> > Cr-Commit-Position: refs/heads/master@{#755543}
>
> TBR=tommycli@chromium.org,ender@google.com
>
> # Not skipping CQ checks because original CL landed > 1 day ago.
>
> Bug: 964049
> Change-Id: I9102a3849018f366b98044921ae711eb8321bbb0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2176653
> Reviewed-by: Ender <ender@google.com>
> Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
> Commit-Queue: Ender <ender@google.com>
> Cr-Commit-Position: refs/heads/master@{#764863}

TBR=tommycli@chromium.org,jdonnelly@chromium.org,ender@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 964049
Change-Id: I4d8bf3f3a879d7a040a37aa72bf7d2c82c9106e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2216790Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Ender <ender@google.com>
Commit-Queue: Ender <ender@google.com>
Cr-Commit-Position: refs/heads/master@{#772002}

components/omnibox/common/omnibox_features.cc

@@ -169,7 +169,13 @@ const base::Feature kAutocompleteTitles{"OmniboxAutocompleteTitles",
 // Returns whether IsInstantExtendedAPIEnabled should be ignored when deciding
 // the number of Google-provided search suggestions.
 const base::Feature kOmniboxDisableInstantExtendedLimit{
-    "OmniboxDisableInstantExtendedLimit", base::FEATURE_DISABLED_BY_DEFAULT};
+  "OmniboxDisableInstantExtendedLimit",
+#if defined(OS_ANDROID)
+      base::FEATURE_ENABLED_BY_DEFAULT
+#else
+      base::FEATURE_DISABLED_BY_DEFAULT
+#endif
+};
 
 // Show the search engine logo in the omnibox on Android (desktop already does
 // this).

testing/variations/fieldtrial_testing_config.json

@@ -3874,7 +3874,6 @@
                         "rounded_edges": "true"
                     },
                     "enable_features": [
-                        "OmniboxDisableInstantExtendedLimit",
                         "OmniboxHistoryQuickProviderAllowButDoNotScoreMidwordTerms",
                         "OmniboxHistoryQuickProviderAllowMidwordContinuations",
                         "OmniboxOnFocusSuggestions"