Switch from int64 to int64_t.

The usage of int64 seems unintentional but it works because int64 is
defined here:
https://cs.chromium.org/chromium/src/third_party/libyuv/include/libyuv/basic_types.h?l=33&rcl=e1f6c1c0b57a9210bb95e88080fa171296210296

This CL switches to int64_t and aligns with the rest of the codebase.

Bug: None
Change-Id: I2292974dbca3692b570214d8bc790336219b151e
Reviewed-on: https://webrtc-review.googlesource.com/87700
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23894}

sdk/android/src/jni/androidmediadecoder.cc

diff --git a/sdk/android/src/jni/androidmediadecoder.cc b/sdk/android/src/jni/androidmediadecoder.cc
index 1ca9e06..96fc748 100644
--- a/sdk/android/src/jni/androidmediadecoder.cc
+++ b/sdk/android/src/jni/androidmediadecoder.cc
@@ -442,7 +442,7 @@
           << frames_received_ << ". Decoded: " << frames_decoded_;
     EnableFrameLogOnWarning();
   }
-  const int64 drain_start = rtc::TimeMillis();
+  const int64_t drain_start = rtc::TimeMillis();
   while ((frames_received_ > frames_decoded_ + max_pending_frames_) &&
          (rtc::TimeMillis() - drain_start) < kMediaCodecTimeoutMs) {
     if (!DeliverPendingOutputs(jni, kMediaCodecPollMs)) {