Refactors platform_view_android_delegate test (flutter#162696)

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Reduce magic number

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Author: chunhtai

engine/src/flutter/shell/platform/android/platform_view_android_delegate/platform_view_android_delegate.cc

@@ -44,12 +44,6 @@ PlatformViewAndroidDelegate::PlatformViewAndroidDelegate(
 void PlatformViewAndroidDelegate::UpdateSemantics(
     const flutter::SemanticsNodeUpdates& update,
     const flutter::CustomAccessibilityActionUpdates& actions) {
-  constexpr size_t kBytesPerNode = 49 * sizeof(int32_t);
-  constexpr size_t kBytesPerChild = sizeof(int32_t);
-  constexpr size_t kBytesPerCustomAction = sizeof(int32_t);
-  constexpr size_t kBytesPerAction = 4 * sizeof(int32_t);
-  constexpr size_t kBytesPerStringAttribute = 4 * sizeof(int32_t);
-
   {
     size_t num_bytes = 0;
     for (const auto& value : update) {

engine/src/flutter/shell/platform/android/platform_view_android_delegate/platform_view_android_delegate.h

@@ -16,6 +16,11 @@ namespace flutter {
 
 class PlatformViewAndroidDelegate {
  public:
+  static constexpr size_t kBytesPerNode = 49 * sizeof(int32_t);
+  static constexpr size_t kBytesPerChild = sizeof(int32_t);
+  static constexpr size_t kBytesPerCustomAction = sizeof(int32_t);
+  static constexpr size_t kBytesPerAction = 4 * sizeof(int32_t);
+  static constexpr size_t kBytesPerStringAttribute = 4 * sizeof(int32_t);
   explicit PlatformViewAndroidDelegate(
       std::shared_ptr<PlatformViewAndroidJNI> jni_facade);
   void UpdateSemantics(

engine/src/flutter/shell/platform/android/platform_view_android_delegate/platform_view_android_delegate_unittests.cc

@@ -23,7 +23,8 @@ TEST(PlatformViewShell, UpdateSemanticsDoesFlutterViewUpdateSemantics) {
   node0.tooltip = "tooltip";
   update.insert(std::make_pair(0, node0));
 
-  std::vector<uint8_t> expected_buffer(196);
+  std::vector<uint8_t> expected_buffer(
+      PlatformViewAndroidDelegate::kBytesPerNode);
   std::vector<std::vector<uint8_t>> expected_string_attribute_args(0);
   size_t position = 0;
   int32_t* buffer_int32 = reinterpret_cast<int32_t*>(&expected_buffer[0]);
@@ -87,7 +88,8 @@ TEST(PlatformViewShell, UpdateSemanticsDoesUpdatelinkUrl) {
   node0.linkUrl = "url";
   update.insert(std::make_pair(0, node0));
 
-  std::vector<uint8_t> expected_buffer(196);
+  std::vector<uint8_t> expected_buffer(
+      PlatformViewAndroidDelegate::kBytesPerNode);
   std::vector<std::vector<uint8_t>> expected_string_attribute_args(0);
   size_t position = 0;
   int32_t* buffer_int32 = reinterpret_cast<int32_t*>(&expected_buffer[0]);
@@ -165,7 +167,10 @@ TEST(PlatformViewShell,
   node0.hintAttributes.push_back(locale_attribute);
   update.insert(std::make_pair(0, node0));
 
-  std::vector<uint8_t> expected_buffer(228);
+  std::vector<uint8_t> expected_buffer(
+      PlatformViewAndroidDelegate::kBytesPerNode +
+      // 1 label attribute + 1 hint attribute.
+      2 * PlatformViewAndroidDelegate::kBytesPerStringAttribute);
   std::vector<std::vector<uint8_t>> expected_string_attribute_args;
   size_t position = 0;
   int32_t* buffer_int32 = reinterpret_cast<int32_t*>(&expected_buffer[0]);
@@ -241,7 +246,8 @@ TEST(PlatformViewShell,
   action0.hint = "hint";
   actions.insert(std::make_pair(0, action0));
 
-  std::vector<uint8_t> expected_actions_buffer(16);
+  std::vector<uint8_t> expected_actions_buffer(
+      PlatformViewAndroidDelegate::kBytesPerAction);
   int32_t* actions_buffer_int32 =
       reinterpret_cast<int32_t*>(&expected_actions_buffer[0]);
   std::vector<std::string> expected_action_strings;