[Impeller] disable GLES tracing unless opted in. (flutter#165887)

GLES tracing may add substantial overhead on some devices. Since this is
only useful when using frame capture tools, and its unlikely anyone that
isn't an engine developer (or who knows how to compile the engine) will
use them - we can turn off with a define.

If there are other usecases we need to cover later this can be made to
use the new flag system.

Author: Jonah Williams

engine/src/flutter/impeller/renderer/backend/gles/proc_table_gles.cc

@@ -129,7 +129,7 @@ ProcTableGLES::ProcTableGLES(  // NOLINT(google-readability-function-size)
 
 #undef IMPELLER_PROC
 
-  if (!description_->HasDebugExtension()) {
+  if (!IP_ENABLE_GLES_LABELING || !description_->HasDebugExtension()) {
     PushDebugGroupKHR.Reset();
     PopDebugGroupKHR.Reset();
     ObjectLabelKHR.Reset();

engine/src/flutter/impeller/renderer/backend/gles/proc_table_gles.h

@@ -14,6 +14,9 @@
 #include "impeller/renderer/backend/gles/description_gles.h"
 #include "impeller/renderer/backend/gles/gles.h"
 
+/// Enable to allow GLES to push/pop labels for usage in GPU traces
+#define IP_ENABLE_GLES_LABELING false
+
 namespace impeller {
 
 const char* GLErrorToString(GLenum value);

engine/src/flutter/impeller/renderer/backend/gles/test/reactor_unittests.cc

@@ -98,13 +98,7 @@ TEST(ReactorGLES, UntrackedHandle) {
 
 TEST(ReactorGLES, NameUntrackedHandle) {
   auto mock_gles_impl = std::make_unique<NiceMock<MockGLESImpl>>();
-
-  EXPECT_CALL(*mock_gles_impl, GenTextures(1, _))
-      .WillOnce([](GLsizei size, GLuint* queries) { queries[0] = 1234; });
-  EXPECT_CALL(*mock_gles_impl,
-              ObjectLabelKHR(_, 1234, _, ::testing::StrEq("hello, joe!")))
-      .Times(1);
-  ON_CALL(*mock_gles_impl, IsTexture).WillByDefault(::testing::Return(GL_TRUE));
+  NiceMock<MockGLESImpl>* raw_mock_gles = mock_gles_impl.get();
 
   std::shared_ptr<MockGLES> mock_gles =
       MockGLES::Init(std::move(mock_gles_impl));
@@ -115,6 +109,13 @@ TEST(ReactorGLES, NameUntrackedHandle) {
     GTEST_SKIP() << "This device doesn't support labelling.";
   }
 
+  EXPECT_CALL(*raw_mock_gles, GenTextures(1, _))
+      .WillOnce([](GLsizei size, GLuint* queries) { queries[0] = 1234; });
+  EXPECT_CALL(*raw_mock_gles,
+              ObjectLabelKHR(_, 1234, _, ::testing::StrEq("hello, joe!")))
+      .Times(1);
+  ON_CALL(*raw_mock_gles, IsTexture).WillByDefault(::testing::Return(GL_TRUE));
+
   auto worker = std::make_shared<TestWorker>();
   auto reactor = std::make_shared<ReactorGLES>(std::move(proc_table));
   reactor->AddWorker(worker);