Don't set -fvisibility=hidden for iOS Debug.

build/config/gcc/BUILD.gn

Index: build/config/gcc/BUILD.gn
diff --git a/build/config/gcc/BUILD.gn b/build/config/gcc/BUILD.gn
index 2c1c61f6afd10d7ad439155642da1576cd47fd5e..c7afcdf544f2b5ad1799cc922ff7ba13f7344a30 100644
--- a/build/config/gcc/BUILD.gn
+++ b/build/config/gcc/BUILD.gn
@@ -18,7 +18,14 @@ import("//build/toolchain/toolchain.gni")
 config("symbol_visibility_hidden") {
   # Note that -fvisibility-inlines-hidden is set globally in the compiler
   # config since that can almost always be applied.
-  cflags = [ "-fvisibility=hidden" ]
+
+  # XCTests inject a dynamic library into an iOS application. If fvisibility
+  # is set to hidden, then some symbols from the application needed by XCTests
+  # may not be available. XCTests are used for iOS integration tests. Make sure
+  # all symbols are exported for Debug configurations on iOS.
+  if (!is_ios || !is_debug) {
+    cflags = [ "-fvisibility=hidden" ]
+  }
 }
 
 # The rpath is the dynamic library search path. Setting this config on a link