(Imported from upstream's 7eeeb49e11)

Here are the performance numbers on a Nexus 9 (32-bit binary):

Before:

Did 4376000 AES-128-GCM (16 bytes) seal operations in 1000016us (4375930.0 ops/sec): 70.0 MB/s
Did 642000 AES-128-GCM (1350 bytes) seal operations in 1001090us (641301.0 ops/sec): 865.8 MB/s
Did 126000 AES-128-GCM (8192 bytes) seal operations in 1001460us (125816.3 ops/sec): 1030.7 MB/s
Did 4120000 AES-256-GCM (16 bytes) seal operations in 1000004us (4119983.5 ops/sec): 65.9 MB/s
Did 547000 AES-256-GCM (1350 bytes) seal operations in 1001165us (546363.5 ops/sec): 737.6 MB/s
Did 99000 AES-256-GCM (8192 bytes) seal operations in 1000027us (98997.3 ops/sec): 811.0 MB/s


After:

Did 4569000 AES-128-GCM (16 bytes) seal operations in 1000011us (4568949.7 ops/sec): 73.1 MB/s
Did 796000 AES-128-GCM (1350 bytes) seal operations in 1000161us (795871.9 ops/sec): 1074.4 MB/s
Did 162000 AES-128-GCM (8192 bytes) seal operations in 1003828us (161382.2 ops/sec): 1322.0 MB/s
Did 4398000 AES-256-GCM (16 bytes) seal operations in 1000001us (4397995.6 ops/sec): 70.4 MB/s
Did 634000 AES-256-GCM (1350 bytes) seal operations in 1001290us (633183.2 ops/sec): 854.8 MB/s
Did 122000 AES-256-GCM (8192 bytes) seal operations in 1005650us (121314.6 ops/sec): 993.8 MB/s


Change-Id: I2fef921069ad174f5651dfe59be262625fb3f7c9
Reviewed-on: https://boringssl-review.googlesource.com/4483
Reviewed-by: Adam Langley <agl@google.com>