SurfaceFlinger: Get rid of String8 in dumpsys

Test: build and gui/ui/renderengine/surfaceflinger tests and compare
dumpsys SurfaceFlinger results
Change-Id: Iafdaf73a0acbbbb8fbafc930ad86285106a07e13
diff --git a/services/surfaceflinger/TimeStats/TimeStats.cpp b/services/surfaceflinger/TimeStats/TimeStats.cpp
index 2b9f5c8..6a5488a 100644
--- a/services/surfaceflinger/TimeStats/TimeStats.cpp
+++ b/services/surfaceflinger/TimeStats/TimeStats.cpp
@@ -33,7 +33,7 @@
 namespace android {
 
 void TimeStats::parseArgs(bool asProto, const Vector<String16>& args, size_t& index,
-                          String8& result) {
+                          std::string& result) {
     ATRACE_CALL();
 
     if (args.size() > index + 10) {
@@ -564,7 +564,7 @@
     return mEnabled.load();
 }
 
-void TimeStats::dump(bool asProto, std::optional<uint32_t> maxLayers, String8& result) {
+void TimeStats::dump(bool asProto, std::optional<uint32_t> maxLayers, std::string& result) {
     ATRACE_CALL();
 
     std::lock_guard<std::mutex> lock(mMutex);
@@ -582,7 +582,7 @@
         result.append(timeStatsProto.SerializeAsString().c_str(), timeStatsProto.ByteSize());
     } else {
         ALOGD("Dumping TimeStats as text");
-        result.append(mTimeStats.toString(maxLayers).c_str());
+        result.append(mTimeStats.toString(maxLayers));
         result.append("\n");
     }
 }
diff --git a/services/surfaceflinger/TimeStats/TimeStats.h b/services/surfaceflinger/TimeStats/TimeStats.h
index 0b24c46..71c3ed7 100644
--- a/services/surfaceflinger/TimeStats/TimeStats.h
+++ b/services/surfaceflinger/TimeStats/TimeStats.h
@@ -24,7 +24,6 @@
 #include <ui/FenceTime.h>
 
 #include <utils/String16.h>
-#include <utils/String8.h>
 #include <utils/Vector.h>
 
 #include <deque>
@@ -35,7 +34,6 @@
 using namespace android::surfaceflinger;
 
 namespace android {
-class String8;
 
 class TimeStats {
     struct FrameTime {
@@ -79,7 +77,7 @@
     TimeStats() = default;
     ~TimeStats() = default;
 
-    void parseArgs(bool asProto, const Vector<String16>& args, size_t& index, String8& result);
+    void parseArgs(bool asProto, const Vector<String16>& args, size_t& index, std::string& result);
     bool isEnabled();
 
     void incrementTotalFrames();
@@ -117,7 +115,7 @@
     void enable();
     void disable();
     void clear();
-    void dump(bool asProto, std::optional<uint32_t> maxLayers, String8& result);
+    void dump(bool asProto, std::optional<uint32_t> maxLayers, std::string& result);
 
     std::atomic<bool> mEnabled = false;
     std::mutex mMutex;