Add type-safe constructors to net::HashValue

BUG=551067

Review URL: https://codereview.chromium.org/1432663002

Cr-Commit-Position: refs/heads/master@{#363051}

net/base/hash_value.cc

@@ -31,6 +31,15 @@ bool SHA256HashValue::Equals(const SHA256HashValue& other) const {
   return memcmp(data, other.data, sizeof(data)) == 0;
 }
 
+HashValue::HashValue(const SHA1HashValue& hash) : HashValue(HASH_VALUE_SHA1) {
+  fingerprint.sha1 = hash;
+}
+
+HashValue::HashValue(const SHA256HashValue& hash)
+    : HashValue(HASH_VALUE_SHA256) {
+  fingerprint.sha256 = hash;
+}
+
 bool HashValue::Equals(const HashValue& other) const {
   if (tag != other.tag)
     return false;

net/base/hash_value.h

@@ -36,6 +36,8 @@ enum HashValueTag {
 
 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) {}