leveldb: Fix the LEVELDB_EXPORT definition in component builds.

LEVELDB_EXPORT is defined in include/leveldb/export.h, and depends on
the definition of LEVELDB_SHARED_LIBRARY. In order for LEVELDB_EXPORT to
be defined consistently, LEVELDB_SHARED_LIBRARY must have the same
definition in leveldb and all targets using it.

Previously, LEVELDB_SHARED_LIBRARY was only defined for component builds
in the //third_party/leveldatabase target. This CL makes the definition
apply to //third_party/leveldatabase dependencies as well.

This CL also renames the //third_party/leveldb target to
//third_party/leveldb_static, to clarify its purpose.

The CL is associated with Bug 823071 because it blocks
https://crrev.com/c/1201856 from landing, which is relevant to that bug.

Bug: 823071
Change-Id: I4216fa52b5f7ed9540ec63be7c16dc7150e9c766
Reviewed-on: https://chromium-review.googlesource.com/1203876
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Chris Mumford <cmumford@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590131}

third_party/leveldatabase/BUILD.gn

@@ -118,17 +118,24 @@ leveldb_sources = [
   "src/util/status.cc",
 ]
 
+config("leveldb_component_config") {
+  if (is_component_build) {
+    # Must be exported to all dependencies so LEVELDB_EXPORT is correctly
+    # defined throughout the component build.
+    defines += [ "LEVELDB_SHARED_LIBRARY" ]
+  }
+}
+
 component("leveldatabase") {
   sources = leveldb_sources
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 
-  if (is_component_build) {
-    defines += [ "LEVELDB_SHARED_LIBRARY" ]
-  }
-
-  public_configs = [ ":leveldb_config" ]
+  public_configs = [
+    ":leveldb_config",
+    ":leveldb_component_config",
+  ]
 
   deps = [
     "//base",
@@ -150,8 +157,14 @@ component("leveldatabase") {
   defines += [ "LEVELDB_COMPILE_LIBRARY" ]
 }
 
-static_library("leveldb") {
-  visibility = [ ":*" ]
+# leveldb does not mark symbols used by tests or its command-line utility as
+# LEVELDB_EXPORT. So, these targets can only be linked statically against the
+# leveldb source code.
+static_library("leveldb_static") {
+  visibility = [
+    ":leveldb_testutil",
+    ":leveldb_leveldbutil",
+  ]
   sources = leveldb_sources
 
   configs -= [ "//build/config/compiler:chromium_code" ]
@@ -191,6 +204,9 @@ if (!is_ios && !is_android) {
   }
 
   static_library("leveldb_testutil") {
+    testonly = true
+    visibility = [ ":*" ]
+
     sources = [
       "src/util/histogram.cc",
       "src/util/histogram.h",
@@ -204,7 +220,7 @@ if (!is_ios && !is_android) {
     configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_deps = [
-      ":leveldb",
+      ":leveldb_static",
     ]
     deps = [
       "//base",
@@ -349,7 +365,7 @@ if (!is_ios && !is_android) {
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     deps = [
-      ":leveldb",
+      ":leveldb_static",
     ]
   }