Fix struct vs. class mismatch in forward definitions

The warnings were being hidden by the use of -isystem to include
frameworks/native/include.

Bug: 31752268
Test: m -j
Change-Id: If2bae8b2fbc4238d6251cdd78bc7b5216684f99d
diff --git a/include/gui/ISurfaceComposer.h b/include/gui/ISurfaceComposer.h
index b46e9e6..dbaa5fe 100644
--- a/include/gui/ISurfaceComposer.h
+++ b/include/gui/ISurfaceComposer.h
@@ -35,8 +35,8 @@
 namespace android {
 // ----------------------------------------------------------------------------
 
-class ComposerState;
-class DisplayState;
+struct ComposerState;
+struct DisplayState;
 struct DisplayInfo;
 struct DisplayStatInfo;
 class HdrCapabilities;
diff --git a/include/gui/SurfaceComposerClient.h b/include/gui/SurfaceComposerClient.h
index 312e02f..6c621ee 100644
--- a/include/gui/SurfaceComposerClient.h
+++ b/include/gui/SurfaceComposerClient.h
@@ -38,7 +38,7 @@
 
 // ---------------------------------------------------------------------------
 
-class DisplayInfo;
+struct DisplayInfo;
 class Composer;
 class HdrCapabilities;
 class ISurfaceComposerClient;
diff --git a/include/ui/Gralloc1On0Adapter.h b/include/ui/Gralloc1On0Adapter.h
index 8beb281..33c2f87 100644
--- a/include/ui/Gralloc1On0Adapter.h
+++ b/include/ui/Gralloc1On0Adapter.h
@@ -104,7 +104,7 @@
 
     // Buffer descriptor lifecycle functions
 
-    class Descriptor;
+    struct Descriptor;
 
     gralloc1_error_t createDescriptor(
             gralloc1_buffer_descriptor_t* outDescriptor);