Mass refactoring: Change JNI #includes to use full paths (content/).

Using relative paths was causing build failures. To create this change:
  * find out/Debug -name *_jni.h -delete
  * find . -name BUILD.gn -exec sed -i '/jni_package =/d' {} \;
  * ninja $ALL_JNI_HEADERS minus third_party, chromecast, cronet, libassistant
  * refactor_jni_includes.py  --out-dir out/Debug
  * fix DEPs files manually
  * split out content changes into this cl

See https://groups.google.com/a/chromium.org/forum/?#!topic/java/MEovGrAwbqI
for discussion on naming scheme.

Bug: 964169
Change-Id: Ife61b2a1c67a32dc7babd6c0e92b6cadca890ad6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1670120
Reviewed-by: Andrew Grieve <[email protected]>
Reviewed-by: Jochen Eisinger <[email protected]>
Commit-Queue: Mohamed Heikal <[email protected]>
Cr-Commit-Position: refs/heads/master@{#671300}
diff --git a/content/shell/browser/shell_android.cc b/content/shell/browser/shell_android.cc
index 0c1834c..3d24dd2b 100644
--- a/content/shell/browser/shell_android.cc
+++ b/content/shell/browser/shell_android.cc
@@ -13,8 +13,8 @@
 #include "base/strings/string_piece.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/content_switches.h"
+#include "content/shell/android/content_shell_jni_headers/Shell_jni.h"
 #include "content/shell/android/shell_manager.h"
-#include "jni/Shell_jni.h"
 
 using base::android::AttachCurrentThread;
 using base::android::ConvertUTF8ToJavaString;