Syntax errors in three network traffic annotations corrected.

Syntax error corrected in network traffic annotations of:
chrome/browser/extensions/install_signer.cc
extensions/browser/updater/extension_downloader.cc

BUG=656607

Review-Url: https://codereview.chromium.org/2900953002
Cr-Commit-Position: refs/heads/master@{#473964}

chrome/browser/extensions/install_signer.cc

@@ -399,7 +399,9 @@ void InstallSigner::GetSignature(const SignatureCallback& callback) {
           chrome_policy {
             ExtensionInstallBlacklist {
               policy_options {mode: MANDATORY}
-              ExtensionInstallBlacklist: '*'
+              ExtensionInstallBlacklist: {
+                entries: '*'
+              }
             }
           }
         })");

extensions/browser/updater/extension_downloader.cc

@@ -506,7 +506,9 @@ void ExtensionDownloader::CreateManifestFetcher() {
           chrome_policy {
             ExtensionInstallBlacklist {
               policy_options {mode: MANDATORY}
-              ExtensionInstallBlacklist: '*'
+              ExtensionInstallBlacklist: {
+                entries: '*'
+              }
             }
           }
         })");
@@ -833,7 +835,9 @@ void ExtensionDownloader::CreateExtensionFetcher() {
           chrome_policy {
             ExtensionInstallBlacklist {
               policy_options {mode: MANDATORY}
-              ExtensionInstallBlacklist: '*'
+              ExtensionInstallBlacklist: {
+                entries: '*'
+              }
             }
           }
         })");