Revert "Roll src/third_party/boringssl/src 0e4a448ab..2507d9e70"

This reverts commit d7a2d953.

Reason for revert: Looks like this broke at least the CFI bot:
https://luci-milo.appspot.com/buildbot/chromium.memory/Linux%20CFI/491
https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.memory%2FLinux_CFI%2F491%2F%2B%2Frecipes%2Fsteps%2Fbrowser_tests%2F0%2Flogs%2FPushMessagingBackgroundModeEnabledBrowserTest.BackgroundModeEnabledWithCommandLine%2F0

./../third_party/boringssl/src/ssl/internal.h:184:10: runtime error: control flow integrity check for type 'bssl::(anonymous namespace)::X25519KeyShare' failed during cast to unrelated type (vtable address 0xffffc815a9ffce5e)
0xffffc815a9ffce5e: note: invalid vtable
<memory cannot be printed>
    #0 0x9aefdf8 in bssl::(anonymous namespace)::X25519KeyShare* bssl::New<bssl::(anonymous namespace)::X25519KeyShare>() third_party/boringssl/src/ssl/internal.h:184:10
    #1 0x9aefcb5 in bssl::SSLKeyShare::Create(unsigned short) third_party/boringssl/src/ssl/ssl_key_share.cc:199:37
    #2 0x9b0bdbd in bssl::ext_key_share_add_clienthello(bssl::SSL_HANDSHAKE*, cbb_st*) third_party/boringssl/src/ssl/t1_lib.cc:2172:19
    #3 0x9b07dc4 in bssl::ssl_add_clienthello_tlsext(bssl::SSL_HANDSHAKE*, cbb_st*, unsigned long) third_party/boringssl/src/ssl/t1_lib.cc:2679:10

Original change's description:
> Roll src/third_party/boringssl/src 0e4a448ab..2507d9e70
> 
> https://boringssl.googlesource.com/boringssl/+log/0e4a448ab8aa66a38593f68d19fa0a2e340833e4..2507d9e7090fcd461f33f3b89bcd56c9a7476a04
> 
> BUG=none
> 
> Change-Id: I34232babbf1adfdb663142b1f6970ed490b16399
> Reviewed-on: https://chromium-review.googlesource.com/586645
> Reviewed-by: Adam Langley <agl@chromium.org>
> Commit-Queue: David Benjamin <davidben@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#490632}

TBR=davidben@chromium.org,agl@chromium.org,svaldez@chromium.org

Change-Id: I155a5550fa70429a33a85654845b9b87c3f11991
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: none
Reviewed-on: https://chromium-review.googlesource.com/593107Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490645}

DEPS

@@ -72,7 +72,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.
-  'boringssl_revision': '2507d9e7090fcd461f33f3b89bcd56c9a7476a04',
+  'boringssl_revision': '0e4a448ab8aa66a38593f68d19fa0a2e340833e4',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling google-toolbox-for-mac
   # and whatever else without interference from each other.

third_party/boringssl/BUILD.generated.gni

@@ -319,7 +319,6 @@ crypto_sources = [
   "src/include/openssl/rsa.h",
   "src/include/openssl/safestack.h",
   "src/include/openssl/sha.h",
-  "src/include/openssl/span.h",
   "src/include/openssl/srtp.h",
   "src/include/openssl/stack.h",
   "src/include/openssl/thread.h",
@@ -353,8 +352,8 @@ ssl_sources = [
   "src/ssl/ssl_buffer.cc",
   "src/ssl/ssl_cert.cc",
   "src/ssl/ssl_cipher.cc",
+  "src/ssl/ssl_ecdh.cc",
   "src/ssl/ssl_file.cc",
-  "src/ssl/ssl_key_share.cc",
   "src/ssl/ssl_lib.cc",
   "src/ssl/ssl_privkey.cc",
   "src/ssl/ssl_session.cc",

third_party/boringssl/BUILD.generated_tests.gni

@@ -69,6 +69,5 @@ crypto_test_sources = [
 
 ssl_test_sources = [
   "src/crypto/test/gtest_main.cc",
-  "src/ssl/span_test.cc",
   "src/ssl/ssl_test.cc",
 ]

third_party/boringssl/BUILD.gn

@@ -22,7 +22,6 @@ config("external_config") {
 config("internal_config") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
   defines = [
-    "BORINGSSL_ALLOW_CXX_RUNTIME",
     "BORINGSSL_IMPLEMENTATION",
     "BORINGSSL_NO_STATIC_INITIALIZER",
     "OPENSSL_SMALL",