Workaround ARM tracing issues for non-component builds.

base/debug/stack_trace.h

Index: base/debug/stack_trace.h
diff --git a/base/debug/stack_trace.h b/base/debug/stack_trace.h
index 23e7b5164b63472409a92e992c5c1095dfa48d26..44c712f2aa934e1de66eb3e29ce5586a56613a5a 100644
--- a/base/debug/stack_trace.h
+++ b/base/debug/stack_trace.h
@@ -24,7 +24,17 @@ struct _CONTEXT;
 
 #if defined(OS_POSIX) && ( \
     defined(__i386__) || defined(__x86_64__) || \
-    (defined(__arm__) && !defined(__thumb__)))
+    (defined(__arm__) && ( \
+        /* We don't normally support thumb mode... */ \
+        !defined(__thumb__) || \
+        /* ...unless we're building non-component build with Clang. \
+           Clang properly sets up fp register, so we can walk stack frames, \
+           but it pushes arbitrary number of registers between fp (r7) and \
+           lr (r14). However in non-component build, where all code is \
+           inside a single mapped region, it's possible to guess lr by \
+           probing up to 7 locations on the stack. */ \
+        (defined(__clang__) && !defined(COMPONENT_BUILD) && \
+            defined(OS_ANDROID)))))
 #define HAVE_TRACE_STACK_FRAME_POINTERS 1
 #else
 #define HAVE_TRACE_STACK_FRAME_POINTERS 0