[layout precompilation] Add testing hook for precompiled layouts

We want to be able to control at a fine grained level whether precompiled
layouts are enabled so we can compare inflation results with and without. This
changes adds a @TestApi method that supports this.

Bug: 111895153
Change-Id: Ib6b62d79a9ca7aefefff8639752aa5838e491038

api/test-current.txt

@@ -2366,6 +2366,10 @@ package android.view {
     method public boolean isSystemGroup();
   }
 
+  public abstract class LayoutInflater {
+    method public void setPrecompiledLayoutsEnabledForTesting(boolean);
+  }
+
   public final class MotionEvent extends android.view.InputEvent implements android.os.Parcelable {
     method public void setActionButton(int);
     method public void setButtonState(int);

core/java/android/view/LayoutInflater.java

@@ -20,6 +20,7 @@ import android.annotation.LayoutRes;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemService;
+import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
 import android.content.Context;
 import android.content.pm.ApplicationInfo;
@@ -399,10 +400,15 @@ public abstract class LayoutInflater {
     }
 
     private void initPrecompiledViews() {
-        // Check if precompiled layouts are enabled by a system property.
-        mUseCompiledView =
-            SystemProperties.getBoolean(USE_PRECOMPILED_LAYOUT_SYSTEM_PROPERTY, false);
+        initPrecompiledViews(
+                SystemProperties.getBoolean(USE_PRECOMPILED_LAYOUT_SYSTEM_PROPERTY, false));
+    }
+
+    private void initPrecompiledViews(boolean enablePrecompiledViews) {
+        mUseCompiledView = enablePrecompiledViews;
+
         if (!mUseCompiledView) {
+            mPrecompiledClassLoader = null;
             return;
         }
 
@@ -431,6 +437,17 @@ public abstract class LayoutInflater {
             }
             mUseCompiledView = false;
         }
+        if (!mUseCompiledView) {
+            mPrecompiledClassLoader = null;
+        }
+    }
+
+    /**
+     * @hide for use by CTS tests
+     */
+    @TestApi
+    public void setPrecompiledLayoutsEnabledForTesting(boolean enablePrecompiledLayouts) {
+        initPrecompiledViews(enablePrecompiledLayouts);
     }
 
     /**