android: Support builds with NDK API versions older than 21 (compat)

The new Linux ProcessInfo implementation uses two macros not readily
available in NDK API versions older than 21 (Android 5.0.0): NT_PRSTATUS
and PR_GETREGSET.

Chrome uses API 21 for 64-bit builds, but uses API 16 for 32-bit builds.

NT_PRSTATUS is normally defined by <elf.h> or by <linux/elf.h>, included
by <elf.h>. Although the definition in <linux/elf.h> is available in
older NDK API versions, this internal header does not mix well with
<elf.h> unless <elf.h> contemplates this combination. As of NDK API 21,
<elf.h> actually delegates most of its work to <linux/elf.h>.

PR_GETREGSET is not available in the NDK at all until API 21. Its
definition is in <linux/ptrace.h>. Most user code should #include
<sys/ptrace.h> instead, which includes <linux/ptrace.h>.

Bug: crashpad:30
Test: crashpad_util_test ProcessInfo.*
Change-Id: I4d07a9964db4665a49bde490e905ae9126880bc5
Reviewed-on: https://chromium-review.googlesource.com/455659
Reviewed-by: Joshua Peraza <jperaza@chromium.org>

compat/android/elf.h

@@ -0,0 +1,25 @@
+// Copyright 2017 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_COMPAT_ANDROID_ELF_H_
+#define CRASHPAD_COMPAT_ANDROID_ELF_H_
+
+#include_next <elf.h>
+
+// Android 5.0.0 (API 21) NDK
+#if !defined(NT_PRSTATUS)
+#define NT_PRSTATUS 1
+#endif
+
+#endif  // CRASHPAD_COMPAT_ANDROID_ELF_H_

compat/android/linux/ptrace.h

@@ -0,0 +1,25 @@
+// Copyright 2017 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_COMPAT_ANDROID_LINUX_PTRACE_H_
+#define CRASHPAD_COMPAT_ANDROID_LINUX_PTRACE_H_
+
+#include_next <linux/ptrace.h>
+
+// Android 5.0.0 (API 21) NDK
+#if !defined(PTRACE_GETREGSET)
+#define PTRACE_GETREGSET 0x4204
+#endif
+
+#endif  // CRASHPAD_COMPAT_ANDROID_LINUX_PTRACE_H_

compat/compat.gyp

@@ -83,6 +83,16 @@
             ],
           },
         }],
+        ['OS=="android"', {
+          'include_dirs': [
+            'android',
+          ],
+          'direct_dependent_settings': {
+            'include_dirs': [
+              'android',
+            ],
+          },
+        }],
       ],
     },
   ],