Replace "const std::string&" with absl::string_view

Ported from internal cl/439097574
diff --git a/tools/BUILD b/tools/BUILD
index d920d86..cc8ec3d 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -33,6 +33,7 @@
         "//lib:quic_trace_cc_proto",
         "@com_google_absl//absl/flags:flag",
         "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings",
         "@com_google_protobuf//:protobuf",
     ],
 )
diff --git a/tools/render/render_trace.cc b/tools/render/render_trace.cc
index a4033e9..8f6bbb2 100644
--- a/tools/render/render_trace.cc
+++ b/tools/render/render_trace.cc
@@ -16,6 +16,7 @@
 #include <string>
 
 #include "absl/flags/parse.h"
+#include "absl/strings/string_view.h"
 #include "google/protobuf/util/json_util.h"
 #include "tools/render/trace_program.h"
 
@@ -25,7 +26,7 @@
 };
 
 namespace {
-InputFormat GuessInputFileFormat(const std::string& filename) {
+InputFormat GuessInputFileFormat(absl::string_view filename) {
   if (filename.find(".json") != std::string::npos) {
     return INPUT_JSON;
   } else {
diff --git a/tools/transform_quic_trace.cc b/tools/transform_quic_trace.cc
index 04c3c20..1513f4a 100644
--- a/tools/transform_quic_trace.cc
+++ b/tools/transform_quic_trace.cc
@@ -21,6 +21,7 @@
 
 #include "absl/flags/flag.h"
 #include "absl/flags/parse.h"
+#include "absl/strings/string_view.h"
 #include "google/protobuf/util/json_util.h"
 #include "lib/quic_trace.pb.h"
 
@@ -45,7 +46,7 @@
 using google::protobuf::util::JsonStringToMessage;
 using google::protobuf::util::MessageToJsonString;
 
-bool IsValidFormatString(const std::string& format) {
+bool IsValidFormatString(absl::string_view format) {
   return format == "protobuf" || format == "json";
 }