Reland: Prevent unsafe narrowing: base/

This relands
https://chromium-review.googlesource.com/c/chromium/src/+/3717404 .

Bug: 1292951
Change-Id: I79a1d884d297903886cf3d8819f8962ba250ccb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3727447
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Owners-Override: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1018684}

ppapi/proxy/ppapi_param_traits.cc

@@ -43,16 +43,15 @@ bool ReadVectorWithoutCopy(const base::Pickle* m,
                            base::PickleIterator* iter,
                            std::vector<T>* output) {
   // This part is just a copy of the the default ParamTraits vector Read().
-  int size;
-  // ReadLength() checks for < 0 itself.
+  size_t size;
   if (!iter->ReadLength(&size))
     return false;
   // Resizing beforehand is not safe, see BUG 1006367 for details.
-  if (INT_MAX / sizeof(T) <= static_cast<size_t>(size))
+  if (size > INT_MAX / sizeof(T))
     return false;
 
   output->reserve(size);
-  for (int i = 0; i < size; i++) {
+  for (size_t i = 0; i < size; i++) {
     T cur;
     if (!ReadParam(m, iter, &cur))
       return false;
@@ -105,7 +104,7 @@ void ParamTraits<PP_Bool>::Log(const param_type& p, std::string* l) {
 void ParamTraits<PP_NetAddress_Private>::Write(base::Pickle* m,
                                                const param_type& p) {
   WriteParam(m, p.size);
-  m->WriteBytes(p.data, static_cast<int>(p.size));
+  m->WriteBytes(p.data, p.size);
 }
 
 // static

ppapi/proxy/url_loader_resource.cc

@@ -238,7 +238,7 @@ void URLLoaderResource::OnPluginMsgSendData(
     const IPC::Message& message) {
   base::PickleIterator iter(message);
   const char* data;
-  int data_length;
+  size_t data_length;
   if (!iter.ReadData(&data, &data_length)) {
     NOTREACHED() << "Expecting data";
     return;