Check types before checking body size in InspectorNetworkAgent code.

EncodedFormData::SizeInBytes doesn't support all possible types (in
particular it DCHECKs on kDataPipe), so by swapping the order of checks
we make sure things actually work correctly.

On of several changes towards making uploading blobs with network service work.

Bug: 821878
Change-Id: I64313bcc390756de6ad0be091d0ab32e9b78ae44
Reviewed-on: https://chromium-review.googlesource.com/962833Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543207}

third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.cpp

@@ -448,13 +448,17 @@ static bool FormDataToString(scoped_refptr<EncodedFormData> body,
   *content = "";
   if (!body || body->IsEmpty())
     return false;
-  if (max_body_size != 0 && body->SizeInBytes() > max_body_size)
-    return true;
 
+  // SizeInBytes below doesn't support all element types, so first check if all
+  // the body elements are of the right type.
   for (const auto& element : body->Elements()) {
     if (element.type_ != FormDataElement::kData)
       return true;
   }
+
+  if (max_body_size != 0 && body->SizeInBytes() > max_body_size)
+    return true;
+
   Vector<char> bytes;
   body->Flatten(bytes);
   *content = String::FromUTF8WithLatin1Fallback(bytes.data(), bytes.size());