android: Only conditionally depend on debugging_buildflags in generate_jni.

Should fix webrtc's use of generate_jni after
https://chromium-review.googlesource.com/c/chromium/src/+/979610

Bug: 799759
Change-Id: I838af362d81036afb8bc493a90c4faa3c4c9b467
Reviewed-on: https://chromium-review.googlesource.com/982010Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546170}

build/config/android/rules.gni

@@ -212,9 +212,18 @@ if (enable_java_templates) {
 
     if (defined(invoker.jni_generator_include)) {
       _jni_generator_include = invoker.jni_generator_include
+      _jni_generator_include_deps = []
     } else {
       _jni_generator_include =
           "//base/android/jni_generator/jni_generator_helper.h"
+      _jni_generator_include_deps = [
+        # Using //base/android/jni_generator/jni_generator_helper.h introduces
+        # a dependency on debugging_buildflags indirectly through
+        # base/android/jni_android.h, which is part of the //base target.
+        # This can't depend directly on //base without causing a dependency
+        # cycle, though.
+        "//base:debugging_buildflags",
+      ]
     }
 
     _foreach_target_name = "${target_name}__jni_gen"
@@ -262,15 +271,8 @@ if (enable_java_templates) {
       if (!defined(public_deps)) {
         public_deps = []
       }
-      public_deps += [
-        ":$_foreach_target_name",
-
-        # This depends on debugging_buildflags indirectly through
-        # base/android/jni_android.h, which is part of the //base target.
-        # This can't depend directly on //base without causing a dependency
-        # cycle, though.
-        "//base:debugging_buildflags",
-      ]
+      public_deps += [ ":$_foreach_target_name" ]
+      public_deps += _jni_generator_include_deps
       public_configs = [ ":jni_includes_${target_name}" ]
     }
   }