Fix breakpad tests dependency to include helper file to runtime_deps.

Change 'deps' to 'data_deps' in order for this helper executable to appear in
'gn desc runtime_deps' list. It is needed to satisfy test isolation
requirements. Besides, this is just a right thing to do since compilation does
not depend on this target.

R=thestig@chromium.org,mark@chromium.org

Bug: 
Change-Id: I5d14e58ce66d2415c59d96d90439d987bbe3a92c
Reviewed-on: https://chromium-review.googlesource.com/806216Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521796}

third_party/breakpad/BUILD.gn

@@ -714,7 +714,6 @@ if (is_linux || is_android) {
 
     deps = [
       ":client",
-      ":linux_dumper_unittest_helper",
       ":processor_support",
       "//build/config:exe_and_shlib_deps",
       "//testing/gmock",
@@ -722,6 +721,10 @@ if (is_linux || is_android) {
       "//testing/gtest:gtest_main",
     ]
 
+    data_deps = [
+      ":linux_dumper_unittest_helper",
+    ]
+
     include_dirs = [
       "linux",  # Use our copy of breakpad_googletest_includes.h
       ".",