FTL: Silence warnings for FTL_FAKE_GUARD

Do not return an lvalue reference to avoid warnings like:

    warning: returning variable 'mPhysicalDisplays' by reference
    requires holding mutex 'mStateLock' exclusively
    [-Wthread-safety-reference-return]

The removal of the lambda means that FTL_FAKE_GUARD(m, e) can no longer
be used in a function that REQUIRES(m), which was redundant. Remove one
such instance in SF.

Bug: 354740314
Bug: 185536303
Flag: EXEMPT compile-time change
Test: m surfaceflinger
Merged-In: I35b029885e9c541c1715c280d4f3542de5096145
Change-Id: I35b029885e9c541c1715c280d4f3542de5096145

Author: Dominik Laskowski

include/ftl/fake_guard.h

@@ -76,12 +76,8 @@ struct [[clang::scoped_lockable]] FakeGuard final {
   FTL_ATTRIBUTE(release_capability(mutex))
 #endif
 
-// The parentheses around `expr` are needed to deduce an lvalue or rvalue reference.
-#define FTL_FAKE_GUARD2(mutex, expr)            \
-  [&]() -> decltype(auto) {                     \
-    const android::ftl::FakeGuard guard(mutex); \
-    return (expr);                              \
-  }()
+#define FTL_FAKE_GUARD2(mutex, expr) \
+    (android::ftl::FakeGuard(mutex), expr)
 
 #define FTL_MAKE_FAKE_GUARD(arg1, arg2, guard, ...) guard
 

services/surfaceflinger/SurfaceFlinger.cpp

@@ -6675,7 +6675,7 @@ void SurfaceFlinger::dumpOffscreenLayers(std::string& result) {
 }
 
 void SurfaceFlinger::dumpHwcLayersMinidumpLockedLegacy(std::string& result) const {
-    for (const auto& [token, display] : FTL_FAKE_GUARD(mStateLock, mDisplays)) {
+    for (const auto& [token, display] : mDisplays) {
         const auto displayId = HalDisplayId::tryCast(display->getId());
         if (!displayId) {
             continue;
@@ -6695,7 +6695,7 @@ void SurfaceFlinger::dumpHwcLayersMinidump(std::string& result) const {
     if (!mLayerLifecycleManagerEnabled) {
         return dumpHwcLayersMinidumpLockedLegacy(result);
     }
-    for (const auto& [token, display] : FTL_FAKE_GUARD(mStateLock, mDisplays)) {
+    for (const auto& [token, display] : mDisplays) {
         const auto displayId = HalDisplayId::tryCast(display->getId());
         if (!displayId) {
             continue;