ppd_provider: pacify presubmit

This change modifies the PpdProvider class to follow the conventions
required by the presubmit checks. The changes are trivial and will cause
no behavioral changes. They pave the way to moving the implementation of
this class into a "deprecated" source file.

Bug: 1025995
Change-Id: I6bb71439e519a7a71c7e8f87639b6f4719b3be96
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935046
Reviewed-by: Sean Kau <skau@chromium.org>
Commit-Queue: Kalvin Lee <kdlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720581}

chromeos/printing/ppd_provider.cc

@@ -726,7 +726,10 @@ class PpdProviderImpl : public PpdProvider {
 
     // Strip shard number from 2 digits following 'index'
     int idx_pos = url_str.find_first_of("0123456789", url_str.find("index-"));
-    return std::stoi(url_str.substr(idx_pos, 2));
+    int shard_number;
+    return base::StringToInt(url_str.substr(idx_pos, 2), &shard_number)
+               ? shard_number
+               : -1;
   }
 
   // Return the URL to get a localized manufacturers map.
@@ -1387,7 +1390,7 @@ class PpdProviderImpl : public PpdProvider {
   // |contents|, clears |contents| otherwise.
   PpdProvider::CallbackResultCode ValidateAndParseManufacturersJSON(
       std::vector<ManufacturersJSON>* contents) {
-    DCHECK(contents != NULL);
+    DCHECK(contents != nullptr);
     contents->clear();
 
     base::Value::ListStorage top_list;
@@ -1421,7 +1424,7 @@ class PpdProviderImpl : public PpdProvider {
   // |contents|, clears |contents| otherwise.
   PpdProvider::CallbackResultCode ValidateAndParsePrintersJSON(
       std::vector<PrintersJSON>* contents) {
-    DCHECK(contents != NULL);
+    DCHECK(contents != nullptr);
     contents->clear();
 
     base::Value::ListStorage top_list;