Add a .gitattributes file to force LF line-endings in .pins files.

This change forces the pins files to use LF line-endings and adds a check to
detect CRLF line-endings that outputs a more helpful error message.

BUG=729553

Review-Url: https://codereview.chromium.org/2941543002
Cr-Commit-Position: refs/heads/master@{#485165}

.gitattributes

@@ -1,2 +1,5 @@
 # Stop Windows python license check presubmit errors by forcing LF checkout.
 *.py  text eol=lf
+
+# Force LF checkout of the pins files to avoid transport_security_state_generator errors.
+/net/http/*.pins  text eol=lf

net/tools/transport_security_state_generator/input_file_parsers.cc

@@ -167,6 +167,12 @@ enum class CertificateParserState {
 }  // namespace
 
 bool ParseCertificatesFile(base::StringPiece certs_input, Pinsets* pinsets) {
+  if (certs_input.find("\r\n") != base::StringPiece::npos) {
+    LOG(ERROR) << "CRLF line-endings found in the pins file. All files must "
+                  "use LF (unix style) line-endings.";
+    return false;
+  }
+
   std::string line;
   CertificateParserState current_state = CertificateParserState::PRE_NAME;