Wrap |kAutofillAssistantDirectActionsName| in the right conditional.

The |kAutofillAssistantDirectActionsName| constant is only declared for
OS_ANDROID in flag_descriptions.h, but is defined for all platforms in
flag_descriptions.cc. This did not trigger a compiler warning because
the definition has an erroneous extern keyword. Remove the extern
keyword and move the constant to the right spot. Do the same for
|kAutofillAssistantDirectActionsDescription|.

Change-Id: I0a8b174a2a27a360a97d0ffa7f5e69c110d2f970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2025248Reviewed-by: Stephane Zermatten <szermatt@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738367}

chrome/browser/flag_descriptions.cc

@@ -149,11 +149,6 @@ const char kAutofillAssistantChromeEntryName[] = "AutofillAssistantChromeEntry";
 const char kAutofillAssistantChromeEntryDescription[] =
     "Initiate autofill assistant from within Chrome.";
 
-extern const char kAutofillAssistantDirectActionsName[] =
-    "Autofill Assistant direct actions";
-extern const char kAutofillAssistantDirectActionsDescription[] =
-    "When enabled, expose direct actions from the Autofill Assistant.";
-
 const char kAutofillCacheQueryResponsesName[] =
     "Cache Autofill Query Responses";
 const char kAutofillCacheQueryResponsesDescription[] =
@@ -2210,6 +2205,11 @@ const char kAutofillAccessoryViewDescription[] =
     "Shows Autofill suggestions on top of the keyboard rather than in a "
     "dropdown.";
 
+const char kAutofillAssistantDirectActionsName[] =
+    "Autofill Assistant direct actions";
+const char kAutofillAssistantDirectActionsDescription[] =
+    "When enabled, expose direct actions from the Autofill Assistant.";
+
 const char kAutofillTouchToFillName[] = "Touch To Fill UI for Passwords";
 const char kAutofillTouchToFillDescription[] =
     "Adds a Touch To Fill sheet to the keyboard accessory which will be shown "