SF: Prime shader cache before boot animation

Primes the shader cache before launching boot animation to avoid
janking when we eventually fall into GLES composition.

Bug: 30040263
Change-Id: I76ba66e92c5e6bb05930c325f384f3b774e91101
diff --git a/services/surfaceflinger/RenderEngine/RenderEngine.cpp b/services/surfaceflinger/RenderEngine/RenderEngine.cpp
index 27357b9..d6a032f 100644
--- a/services/surfaceflinger/RenderEngine/RenderEngine.cpp
+++ b/services/surfaceflinger/RenderEngine/RenderEngine.cpp
@@ -436,6 +436,13 @@
     return config;
 }
 
+
+void RenderEngine::primeCache() const {
+    // Getting the ProgramCache instance causes it to prime its shader cache,
+    // which is performed in its constructor
+    ProgramCache::getInstance();
+}
+
 // ---------------------------------------------------------------------------
 }; // namespace android
 // ---------------------------------------------------------------------------