[android] Use jni.hpp in http_request_android.cpp

platform/android/src/attach_env.cpp

@@ -0,0 +1,22 @@
+#include "attach_env.hpp"
+#include "jni.hpp"
+
+namespace mbgl {
+namespace android {
+
+UniqueEnv AttachEnv() {
+    JNIEnv* env = nullptr;
+    jint err = theJVM->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6);
+
+    switch (err) {
+    case JNI_OK:
+        return UniqueEnv(env, JNIEnvDeleter(*theJVM, false));
+    case JNI_EDETACHED:
+        return UniqueEnv(jni::AttachCurrentThread(*theJVM).release(), JNIEnvDeleter(*theJVM, true));
+    default:
+        throw std::system_error(err,  jni::ErrorCategory());
+    }
+}
+
+}
+}