Fully qualify googletest symbols.

Semi-automatically created with:

git grep -l " testing::" | xargs sed -i "s/ testing::/ ::testing::/g"
git grep -l "(testing::" | xargs sed -i "s/(testing::/(::testing::/g"
git cl format

After this, two .cc files failed to compile and I have fixed them
manually.

Bug: webrtc:10523
Change-Id: I4741d3bcedc831b6c5fdc04485678617eb4ce031
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132018
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27526}
diff --git a/rtc_base/strings/string_builder_unittest.cc b/rtc_base/strings/string_builder_unittest.cc
index 6d8b9f2..84717ad 100644
--- a/rtc_base/strings/string_builder_unittest.cc
+++ b/rtc_base/strings/string_builder_unittest.cc
@@ -67,7 +67,7 @@
   EXPECT_DEATH(sb << msg, "");
 #else
   sb << msg;
-  EXPECT_THAT(sb.str(), testing::StrEq("Thi"));
+  EXPECT_THAT(sb.str(), ::testing::StrEq("Thi"));
 #endif
 }
 
@@ -80,7 +80,7 @@
   EXPECT_DEATH(sb << msg, "");
 #else
   sb << msg;
-  EXPECT_THAT(sb.str(), testing::StrEq("12A"));
+  EXPECT_THAT(sb.str(), ::testing::StrEq("12A"));
 #endif
 }
 
@@ -96,7 +96,7 @@
   // the append has no effect or that it's truncated at the point where the
   // buffer ends.
   EXPECT_THAT(sb.str(),
-              testing::AnyOf(testing::StrEq(""), testing::StrEq("-12")));
+              ::testing::AnyOf(::testing::StrEq(""), ::testing::StrEq("-12")));
 #endif
 }
 
@@ -109,7 +109,7 @@
 #else
   sb << num;
   EXPECT_THAT(sb.str(),
-              testing::AnyOf(testing::StrEq(""), testing::StrEq("123.")));
+              ::testing::AnyOf(::testing::StrEq(""), ::testing::StrEq("123.")));
 #endif
 }
 
@@ -122,7 +122,7 @@
   EXPECT_DEATH(sb << msg, "");
 #else
   sb << msg;
-  EXPECT_THAT(sb.str(), testing::StrEq("123"));
+  EXPECT_THAT(sb.str(), ::testing::StrEq("123"));
 #endif
 }
 
@@ -135,7 +135,7 @@
   EXPECT_DEATH(sb << num, "");
 #else
   sb << num;
-  EXPECT_THAT(sb.str(), testing::StrEq("xyz"));
+  EXPECT_THAT(sb.str(), ::testing::StrEq("xyz"));
 #endif
 }
 
@@ -157,7 +157,7 @@
   sb << 1 << ":" << 2.1 << ":" << 2.2f << ":" << 78187493520ll << ":"
      << 78187493520ul;
   EXPECT_THAT(sb.str(),
-              testing::MatchesRegex("1:2.10*:2.20*:78187493520:78187493520"));
+              ::testing::MatchesRegex("1:2.10*:2.20*:78187493520:78187493520"));
 }
 
 TEST(StringBuilder, Format) {