Remove residual support for SHA-1 public key pins.

net/base/hash_value.h

Index: net/base/hash_value.h
diff --git a/net/base/hash_value.h b/net/base/hash_value.h
index 873378246671e07002e4b4a7223d1a5de660627e..4a1aed30c32d42062cee96e7ff5dc6fb9a0467c4 100644
--- a/net/base/hash_value.h
+++ b/net/base/hash_value.h
@@ -43,16 +43,14 @@ inline bool operator!=(const SHA256HashValue& lhs, const SHA256HashValue& rhs) {
 }
 
 enum HashValueTag {
-  HASH_VALUE_SHA1,
   HASH_VALUE_SHA256,
 };
 
 class NET_EXPORT HashValue {
  public:
-  explicit HashValue(const SHA1HashValue& hash);
   explicit HashValue(const SHA256HashValue& hash);
   explicit HashValue(HashValueTag tag) : tag(tag) {}
-  HashValue() : tag(HASH_VALUE_SHA1) {}
+  HashValue() : tag(HASH_VALUE_SHA256) {}
 
   // Serializes/Deserializes hashes in the form of
   // <hash-name>"/"<base64-hash-value>