Use String8/16 c_str [graphics]

Bug: 295394788
Test: make checkbuild
Change-Id: I69aa06b109c2f40ecf40441cbbb0dfa3e1aa99a1
Merged-In: I69aa06b109c2f40ecf40441cbbb0dfa3e1aa99a1
diff --git a/services/surfaceflinger/tests/utils/ScreenshotUtils.h b/services/surfaceflinger/tests/utils/ScreenshotUtils.h
index f879430..b75cf08 100644
--- a/services/surfaceflinger/tests/utils/ScreenshotUtils.h
+++ b/services/surfaceflinger/tests/utils/ScreenshotUtils.h
@@ -161,7 +161,7 @@
             String8 err(String8::format("pixel @ (%3d, %3d): "
                                         "expected [%3d, %3d, %3d], got [%3d, %3d, %3d]",
                                         x, y, r, g, b, pixel[0], pixel[1], pixel[2]));
-            EXPECT_EQ(String8(), err) << err.string();
+            EXPECT_EQ(String8(), err) << err.c_str();
         }
     }