[Autofill] Fill from the last digits when filling a phone number with a maximum length.

components/autofill/core/browser/phone_number.h

Index: components/autofill/core/browser/phone_number.h
diff --git a/components/autofill/core/browser/phone_number.h b/components/autofill/core/browser/phone_number.h
index 8d50d479a364b0fccb90e791caa0df6ab44af761..9236e2fbf14783160868b977e8212127aef9f438 100644
--- a/components/autofill/core/browser/phone_number.h
+++ b/components/autofill/core/browser/phone_number.h
@@ -47,6 +47,10 @@ class PhoneNumber : public FormGroup {
   static const size_t kSuffixOffset = 3;
   static const size_t kSuffixLength = 4;
 
+  // The size of a phone number consisting of the city code followed by the
+  // prefix and suffix portions of the phone number.
+  static const size_t kCityAndNumberLength = 10;
+
   // The class used to combine home phone parts into a whole number.
   class PhoneCombineHelper {
    public: