[AF] Turn Off Autofill When Autocomplete=off and No Server Data

Overwrite the overall predicted field type to UNKNOWN_TYPE when there
is no server data for this field, and the autocomplete attribute is
set to off.

Testing:
Added unit tests with flag ON and OFF.
Tested manually to see that the issue seen in crbug.com/867995 is
fixed.

Bug: 949783
Change-Id: I0f3071edf30019aba5c374a866c3f9506090d715
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1554048
Commit-Queue: Fabio Tirelo <[email protected]>
Reviewed-by: Fabio Tirelo <[email protected]>
Auto-Submit: Sebastien Lalancette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#648666}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 7aa9dae..8a776d58 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -4030,6 +4030,11 @@
      FEATURE_VALUE_TYPE(features::kInSessionPasswordChange)},
 #endif  // OS_CHROMEOS
 
+    {"autofill-off-no-server-data",
+     flag_descriptions::kAutofillOffNoServerDataName,
+     flag_descriptions::kAutofillOffNoServerDataDescription, kOsAll,
+     FEATURE_VALUE_TYPE(autofill::features::kAutofillOffNoServerData)},
+
     {"enable-portals", flag_descriptions::kEnablePortalsName,
      flag_descriptions::kEnablePortalsDescription, kOsAll,
      FEATURE_VALUE_TYPE(blink::features::kPortals)},