Implement time functions for Fuchsia.

Implement GetProcessCpuTimeNanos and GetThreadCpuTimeNanos for Fuchsia.
This is needed for the tests call_perf_tests and
video_pc_full_stack_tests on Fuchsia.

Bug: fuchsia:115601
Change-Id: Idd10db93d4087d10896ae3fde6abbc37176f625e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/290920
Reviewed-by: Christoffer Jansson <jansson@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Sarah Pham <smpham@google.com>
Cr-Commit-Position: refs/heads/main@{#39119}

rtc_base/cpu_time.cc

diff --git a/rtc_base/cpu_time.cc b/rtc_base/cpu_time.cc
index a8e542b..d3fee50 100644
--- a/rtc_base/cpu_time.cc
+++ b/rtc_base/cpu_time.cc
@@ -26,6 +26,10 @@
 #include <unistd.h>
 #elif defined(WEBRTC_WIN)
 #include <windows.h>
+#elif defined(WEBRTC_FUCHSIA)
+#include <lib/zx/process.h>
+#include <lib/zx/thread.h>
+#include <zircon/status.h>
 #endif
 
 #if defined(WEBRTC_WIN)
@@ -39,10 +43,17 @@
 
 int64_t GetProcessCpuTimeNanos() {
 #if defined(WEBRTC_FUCHSIA)
-  RTC_LOG_ERR(LS_ERROR) << "GetProcessCpuTimeNanos() not implemented";
-  return 0;
-#else
-#if defined(WEBRTC_LINUX)
+  zx_info_task_runtime_t runtime_info;
+  zx_status_t status =
+      zx::process::self()->get_info(ZX_INFO_TASK_RUNTIME, &runtime_info,
+                                    sizeof(runtime_info), nullptr, nullptr);
+  if (status == ZX_OK) {
+    return runtime_info.cpu_time;
+  } else {
+    RTC_LOG_ERR(LS_ERROR) << "get_info() failed: "
+                          << zx_status_get_string(status);
+  }
+#elif defined(WEBRTC_LINUX)
   struct timespec ts;
   if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == 0) {
     return ts.tv_sec * kNumNanosecsPerSec + ts.tv_nsec;
@@ -76,15 +87,21 @@
       false, "GetProcessCpuTimeNanos() platform support not yet implemented.");
 #endif
   return -1;
-#endif  // defined(WEBRTC_FUCHSIA)
 }
 
 int64_t GetThreadCpuTimeNanos() {
 #if defined(WEBRTC_FUCHSIA)
-  RTC_LOG_ERR(LS_ERROR) << "GetThreadCpuTimeNanos() not implemented";
-  return 0;
-#else
-#if defined(WEBRTC_LINUX)
+  zx_info_task_runtime_t runtime_info;
+  zx_status_t status =
+      zx::thread::self()->get_info(ZX_INFO_TASK_RUNTIME, &runtime_info,
+                                   sizeof(runtime_info), nullptr, nullptr);
+  if (status == ZX_OK) {
+    return runtime_info.cpu_time;
+  } else {
+    RTC_LOG_ERR(LS_ERROR) << "get_info() failed: "
+                          << zx_status_get_string(status);
+  }
+#elif defined(WEBRTC_LINUX)
   struct timespec ts;
   if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) == 0) {
     return ts.tv_sec * kNumNanosecsPerSec + ts.tv_nsec;
@@ -123,7 +140,6 @@
       false, "GetThreadCpuTimeNanos() platform support not yet implemented.");
 #endif
   return -1;
-#endif  // defined(WEBRTC_FUCHSIA)
 }
 
 }  // namespace rtc