Roll Fuchsia SDK to latest

This rolls to CIPD package versions:
macOS SDK: pWygawI3vBzP9dYloEvKka8r1p0NpLLZzZQ-yMYI1UIC
Linux SDK: L_ORUWXyDEC29pSiSyKIwGqcFMQFsV91E3h_wPbUIUkC

Applies two breaking changes from the SDK:
* `zx_clock_get_new()` has been eliminated and replaced with
  `zx_clock_get()`.
* Scenic `Metrics` no longer supports operator==; instead we use
  `fidl::Equals()`.

Author: cbracken

DEPS

@@ -126,7 +126,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + '5383f9c6ad891c28d0d2f3103864ff6ff377ceff',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'ad2256a52991dd857aea2aba3240604543ffe232',
 
    # Fuchsia compatibility
    #
@@ -480,7 +480,7 @@ deps = {
      'packages': [
        {
         'package': 'fuchsia/sdk/core/mac-amd64',
-        'version': 'Cx51FRV5TCoqQ9nfs4E2QMfYkJ1JWt7arQXhV01tr7cC'
+        'version': 'pWygawI3vBzP9dYloEvKka8r1p0NpLLZzZQ-yMYI1UIC'
        }
      ],
      'condition': 'host_os == "mac"',
@@ -500,7 +500,7 @@ deps = {
      'packages': [
        {
         'package': 'fuchsia/sdk/core/linux-amd64',
-        'version': 'udf6w2VmM5E8PyQm5ggugW_jjiEdWs-Xl6efeLf2JdkC'
+        'version': 'L_ORUWXyDEC29pSiSyKIwGqcFMQFsV91E3h_wPbUIUkC'
        }
      ],
      'condition': 'host_os == "linux"',

shell/platform/fuchsia/dart-pkg/zircon/sdk_ext/system.cc

@@ -477,7 +477,7 @@ Dart_Handle System::VmoMap(fml::RefPtr<Handle> vmo) {
 
 uint64_t System::ClockGet(uint32_t clock_id) {
   zx_time_t result = 0;
-  zx_clock_get_new(clock_id, &result);
+  zx_clock_get(clock_id, &result);
   return result;
 }
 

shell/platform/fuchsia/flutter/platform_view.cc

@@ -293,7 +293,7 @@ void PlatformView::OnScenicEvent(
       case fuchsia::ui::scenic::Event::Tag::kGfx:
         switch (event.gfx().Which()) {
           case fuchsia::ui::gfx::Event::Tag::kMetrics: {
-            if (event.gfx().metrics().metrics != scenic_metrics_) {
+            if (!fidl::Equals(event.gfx().metrics().metrics, scenic_metrics_)) {
               scenic_metrics_ = std::move(event.gfx().metrics().metrics);
               metrics_changed_callback_(scenic_metrics_);
               UpdateViewportMetrics(scenic_metrics_);