Set caches directory on Fuchsia (#18321)

fml/platform/fuchsia/paths_fuchsia.cc

diff --git a/fml/platform/fuchsia/paths_fuchsia.cc b/fml/platform/fuchsia/paths_fuchsia.cc
index 1b03307..e26b32d 100644
--- a/fml/platform/fuchsia/paths_fuchsia.cc
+++ b/fml/platform/fuchsia/paths_fuchsia.cc
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "flutter/fml/file.h"
 #include "flutter/fml/paths.h"
 
 namespace fml {
@@ -12,8 +13,7 @@
 }
 
 fml::UniqueFD GetCachesDirectory() {
-  // Unsupported on this platform.
-  return {};
+  return OpenDirectory("/cache", false, fml::FilePermission::kRead);
 }
 
 }  // namespace paths

shell/platform/fuchsia/flutter/meta/flutter_aot_product_runner.cmx

diff --git a/shell/platform/fuchsia/flutter/meta/flutter_aot_product_runner.cmx b/shell/platform/fuchsia/flutter/meta/flutter_aot_product_runner.cmx
index 914c22b..16232df 100644
--- a/shell/platform/fuchsia/flutter/meta/flutter_aot_product_runner.cmx
+++ b/shell/platform/fuchsia/flutter/meta/flutter_aot_product_runner.cmx
@@ -6,7 +6,8 @@
     "features": [
       "config-data",
       "root-ssl-certificates",
-      "vulkan"
+      "vulkan",
+      "isolated-cache-storage"
     ],
     "services": [
       "fuchsia.accessibility.SettingsManager",

shell/platform/fuchsia/flutter/meta/flutter_aot_runner.cmx

diff --git a/shell/platform/fuchsia/flutter/meta/flutter_aot_runner.cmx b/shell/platform/fuchsia/flutter/meta/flutter_aot_runner.cmx
index 11ba40d..4c49f57 100644
--- a/shell/platform/fuchsia/flutter/meta/flutter_aot_runner.cmx
+++ b/shell/platform/fuchsia/flutter/meta/flutter_aot_runner.cmx
@@ -6,7 +6,8 @@
     "features": [
       "config-data",
       "root-ssl-certificates",
-      "vulkan"
+      "vulkan",
+      "isolated-cache-storage"
     ],
     "services": [
       "fuchsia.accessibility.SettingsManager",

shell/platform/fuchsia/flutter/meta/flutter_jit_product_runner.cmx

diff --git a/shell/platform/fuchsia/flutter/meta/flutter_jit_product_runner.cmx b/shell/platform/fuchsia/flutter/meta/flutter_jit_product_runner.cmx
index af0c724..e66eda1 100644
--- a/shell/platform/fuchsia/flutter/meta/flutter_jit_product_runner.cmx
+++ b/shell/platform/fuchsia/flutter/meta/flutter_jit_product_runner.cmx
@@ -7,7 +7,8 @@
       "config-data",
       "deprecated-ambient-replace-as-executable",
       "root-ssl-certificates",
-      "vulkan"
+      "vulkan",
+      "isolated-cache-storage"
     ],
     "services": [
       "fuchsia.accessibility.SettingsManager",

shell/platform/fuchsia/flutter/meta/flutter_jit_runner.cmx

diff --git a/shell/platform/fuchsia/flutter/meta/flutter_jit_runner.cmx b/shell/platform/fuchsia/flutter/meta/flutter_jit_runner.cmx
index af0c724..e66eda1 100644
--- a/shell/platform/fuchsia/flutter/meta/flutter_jit_runner.cmx
+++ b/shell/platform/fuchsia/flutter/meta/flutter_jit_runner.cmx
@@ -7,7 +7,8 @@
       "config-data",
       "deprecated-ambient-replace-as-executable",
       "root-ssl-certificates",
-      "vulkan"
+      "vulkan",
+      "isolated-cache-storage"
     ],
     "services": [
       "fuchsia.accessibility.SettingsManager",

testing/fuchsia/meta/fuchsia_test.cmx

diff --git a/testing/fuchsia/meta/fuchsia_test.cmx b/testing/fuchsia/meta/fuchsia_test.cmx
index 7239603..2d9addc 100644
--- a/testing/fuchsia/meta/fuchsia_test.cmx
+++ b/testing/fuchsia/meta/fuchsia_test.cmx
@@ -5,7 +5,8 @@
   "sandbox": {
     "features": [
       "vulkan",
-      "deprecated-ambient-replace-as-executable"
+      "deprecated-ambient-replace-as-executable",
+      "isolated-cache-storage"
     ],
     "services": [
       "fuchsia.accessibility.semantics.SemanticsManager",